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NASA Contractor Report I05003
(H&OA-CB-1550U3-Vo_-1) _+OWn_Y_(J.LJJ'_..NULaLt_I_ dt+_-1q059, AZJ_P_Z& SUilVB_e VOLUH]_I F_, li@po_t (Low
BIl@¢qy TL'on,uporf, _Jg_t_m_) 105 pHC AOS/HP A01 C_¢L IOA ULL_I_
' dJ/O_ OO_d7
LOW REYNOLDSNUMBER/_IRFOILSURVEY
VOLUME I
B. H. Carmichael _(
LOW ENERGY TK_NSPORTATIONSYSTEMS /
CaplstranoBeach;California 92.624
' ""_se Order L-4059B981
NaltonalAeronauticsandSpaceAdministration
LI_p_ Fleem_.hc+mteHampton,Virginia23665
+ ;+-+-_+-_+ :+++ , + +.... + , o + • , , . .o . + , .... _ .............. _ .... "%,_.......... .......... + -+_"++'+_\-. " '+ + __ ......... ..... +._ , , , , , ,,,,,,, + , +i, ,++
00000002
https://ntrs.nasa.gov/search.jsp?R=19820006186 2019-02-04T09:52:56+00:00Z
!PREFACI:
Tile1ocatlmland cnllm:timl_f tim.lar_]em_,h_)raf _meful references
p(_rtalnin.qto thls l_Ighlysp_:_l_11zedfi_,Idwas _.xpmllt_dthr(}ll_lhthe 1
golmrou_and wholelleartedco_p_.ration_f many enthuslastlcres_.;arcllers.
The extensive_irf(}ildo_i_n alldt_.stil1.qby lI)'_.Altl_aus,Epplerand j!
Wortm_mnof StuttgartUniversity,those of Dr. wm Inge,and his associ_ites
at Delft University,The Netherlands,_md those of Dr. Muel]Qra,d his
associatesat the Universityof Notre Dame are currentand most useful.
AlthoughNASA Langleyis not active in the criticalReynoldsnumber field,,!
discussionswith Dr. Pfennlnger,H. Phillips,and Dan Seinersand Harry i
Sheaf of thatfacilityhave been helpful. Additionalusefuldata have06
been obtainedthrl_ughDr. Kramerof GottingenUniversity,Dr. Marsdenof
the Universityof Alberta,Dr. Miley of Texas A&M, Dr. E(.Ig!estonof the
Universityof WesternOntarlo_ Larrabeeand Derilla of Mas._achusettS
Instituteo'_Technology,a_d Patrickof CranfieldUniversity.
Aid was also receivedfrom Zipkinand Dr. Roy Smith of GeneralElectric
Corporation.Jolm McMastersof BoeingAircraft,Bob Liebeckof Douglas
Aircraft,and Russ Osborn_of Wright Field
The scientificfree flightmeasurementsof model aircraftbuilders,
MaxlmilllanHacklingerof Germany.[illbertHoffmann,Andy Buaer, and "
Blain Rawdonof the UnitedStateshave been inspiring°
Meeting_nd talkingwith Frank Zaic, whose Model AircraftYearbooks
have disseminatedthe latesttechnologyto model aircraftbuildersthrough-
out the world for half a centurewas a great joy and prlvilege. Discusslons
and c_)rrespondencewltl_expertmodel builderssu_:has Blanchard,¢hampine,*!
.* llmman,Hines, Isaacson,Mouser,Meier, Ko, Pressnell,Gioskleng,Gale,
i i
00000002-TSA03
Reld,Wagner,White,and Xenakishaveh_Ipedto make th_ limltati_s
of laboraturydevelopedmaximump_rfo_anceairfoilswhenenceunterlng
the realworldaf rouohalr dynamicfreefllghtpalnfullyclear, The
keenobservationalpowerBand empiricaldevelopment_by freeflight :;I
modelbuilder_havealreadyarrivedat a hlghtechnlcalplateau,
ii
O0000002-TSA04
c.\
-)
L_O_,._REYNOLDSN.U.MBE_RAIRFOIL DA_TA.sURVE_y
TABLE.OF CONTENTS_
List of Illustrations v
Nom(_nclature vliix
Sumnlary
I Brlof Reviewof ApplicableAerodynanlicPrinciple_ I
II Changesin Flow Phenomenaand Wing Design Technique 7With Inc,'easingRNFlow PhenomenaBibliography 14
Iil S.tateof Knowledgeon Fluid Flow Separation 15
Introduction 15
Chronology 16
Discussion 19
FlowSeparationBibliography 43
IV Low ReynoldsNumberAirfoilCharacteristics 46
(A) LaboratoryTest Data 46
HistoricalReview 46
Chronology 53
Discussion 57
Bibliography 67
(B) Discussionof Free FlightTesting 71
Chronology 73
Free FlightBibliography 75
(C) Low ReynoldsNumberAirfoilDesign 77 :
AirfoilDesignBibliography 81
(D) Books o_ TechnicalAeromodelling 84
V BoundaryLayerTrippingDevices 85 '
(A) HistoricalReview 85
(B) VariousMethodsof BoundaryLayer Tripping 86 !
(C) Uiscussion 88
(D) Bibliography 96
iii
• 't
00000002-TSA05
PREOEDINGPAGEBLANKNOT
Listof lllgstratlQns
II-I- The Realmof Reynolds 8
III-1 - LaminarBubbleGeometry 28
-= - SchematicDiagramof LaminarSeparation Bubble 29
-3 - t.amtnarSeparation Prediction 30
-4 - Reparation Streamline Angle 31
-5 - SeparationStreamlineAngle 32
-6 - TransitionBubbleLength 33
-7 - LaminarPart of BubbleLength 34
-8 - TotalBubbleLength 35
-9 - CriticalBurstingPressureCoefficient 36
-10-BubbleEffectson PressureDistribution 37
-11-BoundaryLayerVelocityProfile 38
-12-BubbleLengthvs. ROs 39
-13-TransitionCriteriaBasedon BubbleHeightand RN 3g
-14-VelocityDistributionsin SeparationBubble 40
-15-PressureDistributionoverSeparatedRegion 41 ,!-16-Variationin ShapeFactorH =_*/0 41 il
-17-Comparisonof CalculatedVelocityDistributions 42 iii
IV-I- AerodynamicCompariSonof TurbulentTunnelData 47 .(withRN increasedto accountfor turbulence)withlow turbulencetunneldata) _'_
-2 - Liftvs Dragand LiftvsdForms 59
-3 - Eppler61 Airfoilin ThreeWindTunnelsat RN = 50,000 61
-4 - Eppler61 Airfoilin Three WindTunnelsat RN = 80,000 63
-5 - Comparisonof Eppler387 ExperimentalPolarsWith 79TheoreticalPredictions
V
•-,'-.
=.._: ._',
00000002-TSA06
V-1 - Various Methods of Boundary Layer Tripplng B7
-2 - Effect of Sound and T.rip Wire on E-51 at Rc - 80,OOD 93
-3 - Effectof Sound and Trip Wire on E.61 at Rc = 50,000 g4-4 - Effectof Sound PressureLevel on Lift in CriticalRange g5
vi
00000002-TSA07
N_enclature
r SYMBOL DESCRIPTION UNITS • •'t .........
c atrFotl chord length ft.
CB drill.I,coefficient_ Dlq . S
CL llft coefficient_,L/q • S
CM pitchingmonlentcoefficient= M/q . S , c
Cp pressurec(_efflcient_ (Pl " Po)/q
Ow wetted area drag coefficient= D/q . Sw
D drag pounds
f camberor maximummean line heightabove chord..1-ine c
g accelerationof gravity ft/sec2
ht heightof bubbleat _ransltien ft.
l Iength ft.
L Iift pounds
Lb total bubblelength _ ft.
m velocitygradientparameter= Yg- cJ.UWK
M pitching moment ft.pounds
Pl local surfacepressure pounds/ft2
Po ambit pressure _ pounds/ft2 •
q fIlghtdynamicpressure= _U=_ pounds/ft2
R reattachmentpoint
Rs arc lengthReynoldsNo. U ._"= _
RN chord ReynoldsNo. : Rc : U_v,_ii
Rtl momentumthicknessReynoldsNo. : --_
R% % at separationpoint : ..J,L._
s arc lengthfrom stagnationpoint ft.
S wing area ft2
viii. !
(
................. "" • " :' . _':'.'.i"-/- ." " ._". " ' ' _t.5"- .... "-'-" " , ....,, • .,- ........ "i
00000002-TSA08
Nomenclature Conttnued
SYMBOL DESCRIPTION UNITS
Sw wetted_rea ft2
SPL sound pressure level db
t maximumairfoll thickness ft.
T transitionpoint
Tu turbulencelevel 'X,IJ_
_i velocityat heighty in the boundarylayer ft/sec
U velocityat outsideedge of the boundarylayer ft/sec
U=, flight velocity ft/sec
V spanwise velocity ft/sec ,
X distancealong strean}direction ft.
AX laminarportionof bubble length ft.
y distancenormal to surface ft.
_ angle of attack - betweenchord line & relativewind deg.
^ incrementof distance ft.6
_* displacementthickness: _ (I- "_) ¢J_' ft. ,
s _ ¢jy 1II momentumthickness= J"-_(/ "O'J ft.
y separationstreamlineangle from surface deg. .,
o pressurerecoverycoefficient- I -
p fluid density pounds sec2ftq
_l absoluteviscosity op_o_u_P,_dssec---r:+-Z-----ft
v kinematicviscosity ft2/sec
viii
:1:2,
00000002-TSA09
SUMMARY
Experimental_erodynamicpropertiesQf two dlmensionalalrfol1._in
the critlcalehordl_n,qthReynold_number rar}qebetween40,000 and 100,000
have been gatho,red from sourcesIn nine countriesof'the world and from
a seven decadetlme period, The differencesIn 'Flaw_havior in this
re!ilmecomparedwlth lower and higherReynoldsnumbersare dlscus._d,
Informationon flow separation,in partlcqlar,the large lamlnarseparation
bubble is discussedIn detail in view of Its importantinfluenceon critical
Reynoldsnumberairfoilbehavior, The shbrtcomingsof applyingtheoretical
boundarylayer computationsfound successfulat higher Reynoldsnumbersto
tt,e criticalregimeare discussed. The large variationIn experimental
aerodynamiccharacteristicneasurementrideto small changesin amblent
turbulence,vibration,and sound level is._..]lustratedwlth experlmentaldata.
The variationin resultsfrom the best availablelaboratoriesand the
problemof realistic laboratorvsimulatio, of free fliqht conditlons is made
clear. The difficultiesin obtainingaccuratedetailedmeasurementsin
free flightare discussed.
Dramaticperformanceimprovementsat criticalReynoldsnumber,achieved .,I
with varioustypes of boundarylayer trippingdevicesare discussed, !i
The includedchronologiesand bibliographiesare intendedto be the :i
"1most completeavailableon this subject,
The aerodynamicparametersof airfoilsin the csiticalReynolds
number rangewill be comparedin the secondvolumeof this study.
ix
00000002-TSA10
I .BRIEF.REVIEW_OFAPPL.,!CABbE,AERODYNAMICPRINCIPLES
Boundary_Laye_tr
A comparativelythin_heet of decelerated fluidoriginatingthrough
frictionalongthesurfaceof solids,
Bound______aryL__aa__?_r- Lamlnar
The conditionfoundat lowerReynold_numbersin whichinterchange
of momentumbetweenadjacentboundary_ayorlevelsdoesne_._.toccur_
Surfacefrlctionand flowgeneratednoiseare lowcomparedto---
BoundaryLayer- Turbulent
The conditionfoundat higherReynoldsnumbersin whichinterchange
of momentumbetweenadjacentboundarylayerlevelsdoesoccur,
Surfacefrictionand flowgeneratednoiseare highcomparedto the
laminarcondition.
Coefficientof Lift
The liftforce(L)of a wing,non-dimensionalizedon the basisof CL =L_..L__-projectedwingarea (S)and flightdynamicpressure(q). _oq
Coefficientof Drag- Profile
Thedragforce(D)of a wing,non-dimensionalizedon thebasisof
projectedwingarea (S)and flightdynamicpressure(q). CD =
Coefficientof Drag- Wetted
The dragforce(D)of a wing,non-dimensionalizedon thebasis =D._.D___CW
of wettedareaSW = 25 and flightdynamicpressure(q). sw.q
Coefficientof Mome,nt
The pitchingmoment(M)of a wing,non-dlmensionallzedon the Mbasisof projectedwingareaS, wingchordc, and fiightdynamic CM =
pressure(q),
L
, I ............... " ' "" * _ I__' I- I "" "
00000002-TSA11
_fflclen.t of Pr_s_,Jr_
The differencebetweenlocal surfacepres_wreat a_y point _n a P'Powing (P) and the free streampressure(Po), non-dimnnBionall;_ed Cp - .....q....by flightdynamicpressure(q),
The mass donBlty|,_c_quAito the weight per unit volumt)dYvldOd. W '_:
by the acce|eratlonof gravity,
Fli ht [)2nam•icPro,_sure
Th_ kl_tic _nergyof the re}ativealrstreamIs equal to the _p.Uproductof one-halfthe i]uid mas_ densityand the squareof q =z.
the flightor free stroa0rlvelocity,
PressureGradiu,nt
The rate of rise or fall of local pressurewith dts.tancealong
the surface _P/as
ReynoldsNumber- Chord
The ratio of inertialto viscousinfluenceson the boundarylayer.
Large valueshelp the boundary_,ayerremainattachedin spite of ,U=cviscous inducedretardationin the face of strong adversepres- Rc • p.....
sure gradients. For a given fluid conditionof densityp and
viscosity _ the Reynoldsnumber is proportionalto the " _ 'I
productof wing chord ,cand true flightspeed U = 1I
,Rey_o]d_sN_umber,_Bou_ndar_y.Layer _I
Predictionof the detailedbehaviorof the boundarylayer is 'e
often correlatedon the basis of either the dlsp_acementthick- R_, U _* i=l - _ •
ness RN R_.., or the momentumthicknessRN R o ' where the U.0 1
local velocityU at the outer edge of the boundarylayer is Re = _ .:isubstitutedfor flightvelocity,
.Separationof the BoundaryLaye_r_:-Laminar
At low Reynoldsnumbersthe frictionretardedflow near the
surfacehas insufficientinertiaor ,_mentumto oppose adverse
pressuregradientsabove a certainlevel,and is actually
reversedin directionand separatesfrom the surfacecausing
large decreasein lift and large increasein drag° At Reynolds
-2-
',..
O0000002-TSA12
numbersbelow about 50,000 there Is Insufficient dtstance foe the
fl_ to reattach prior tQ the.-traLl._ng (edge,,
tt q_La na rAt _umewhathtgheP Reynolden,mber_ tt ls pe_stble fQr the
Separated laminar be.ndary layer to go throggt_trafleltlon toturbulent flaw _ a free wake, _nd tl_._nreattach to the s.rfa_e
a_ a turbulent boundary layer prior to the tratltng edgn_ The
rngton whore tht_ complexphenomenatako_ placn t_ call_d thelamtnar separation b,bble, and t_ so Important for the range
50,000 _ RC ", 4,000,000 that; an orltlro soctton of th'l_ report(Ill) wlll be devoted 1;oit.
Se_p,ra,tt,o,no,f t;,'hpBPu,,dary L_yo_P._Turbulent
It iS also posstble i_ora turbulent boundarylayer to separate,causinga decrease in llftand a lai"ge..tncrease tn drag,. Thts
can be delayed by increases in chord Reynoldsnumber,extensive
laminar flow aheadof the start of pressure rise, and shapingthe atrt'otl to produce an tntttal steep rise in pressure white
the boundarylayer is stt11 relatively thin, then gradually
decreasing the pressure gradient as the boundary layer thickens°
5u_ctionB_oundarjtLa_..er_Cpntrog.].l
Aerodynamicadvantagescan be achievedby suckingawaythe lower
retardedlayer_.Thismethodcan be usedto obtainlargeincreases
in maximumliftcoefficient,or in thecaseof carefullydistri-
butedsuctionto retainattachedlaminarboundarylayerseven in
the presenceof strong adverse longitudinal and transverse
pressure gradients to theoretically unlimited values of Reynoldsnumber_
T.ht.ckne.ss.: I)t_placement
The boundarylayer displacement thickness 6 * is the degree by
which the potential flow is displaced terom,the wall by the
boundarylayer_ 6 * can also be thought of as the Pequtred _* "/o (1- dyheight of a layer whichhas lostall of itsvelocitywitha
massflowlossequalto thatintegratedthroughthe actual
boundarylayer.
-3-
=:_: ' "_._'. 'c"_ " .-: " . .=:_....... : _: !_'.-},_". -""_T"....... ".;.';..= ..... _'._Z..... 'Z..'.-'"" ,.:....-....... .,;,..-.1.,t_.,,jL':_--:''- .............. --"- w
00000002-TSA13
Thickness- Momentum
The boundarylayer mQmentumthickness -g- is l_e height Qf a
completely stagnant layer which wo.ld have the _amelos_ in o - ft_ _1-(1" _ )dymomentumas that integrated through the act,el boundary layer.
Themomentum1o_ t_ equal to the drag,
Thlckne,_ _ Klnett.c Ert_r{Lyor Dt._tp_atton
6.Tht_ t:hickno_Gfo]low;, the ,ame roa,ontn9 a._above hilt 1II terflL_ _ _ J'o _'l.'-'tdyof Io_ in klnetlcenorfjy,,It Is usefulifl certain1correlatlve : |_'zlwork,
Transition _ Boundar_La_r
At sufflcientlyhighcomblnation,_of Ruyno](Jsnumberand
disturbancelevels,the boundarylayerwhichstartsoff in
thelaminarstategoesthrougha complextransltlon.tothe
fullyturbulentstate. It Is notgenerallyrealizedJust
how far thisprocesscanbe delayedby reducingdisturbance
in theenvironmentor thoseintroducedby thevehicle.The
earlierestabllshedflatplatetransitionlineis still
copiedfromtextbookto textbookshowinga transitionat
RX = 320,000 in spite of the fact that RX = 3 X 106 was jtRX _ 5 X lO6 morerecently.If nowa I
achievedin 1940and
strongfavorablepressuregradientis introduced,as on the _i
forwardpa-tof thicklowdr._gairfoilsor low lengthto !
diameterratiobodiesof revolution,thetransitionlength J
Reynoldsrumberhasbeenraisedto 45,000,000and forsome _icasescould be evenhigher, As statedpreviously,thereis !W
no theoreticallimitto laminarlengthReynoldsnumberwith 1
distributedsuctionflowcontrol, i
Tripp!ngof theBoundaryLa},.er
Tlleboundary]ayercan be artificiallyinducedto changestate ,i
fromthe laminarto the turbulentcaseby introductionof /variouseddyproducers_.itherin theflowaheadof thewing
or on thewingsurfaceitself.Thisis doneto mitigatethe I
effectsof the laminarseparationpreviouslydiscussed.In iI
_4 _
• •....:, - ,..':_:-.:_. -_.:-.._..:-.o..-'-..'_'..-.--..'._--'_.:.,_,.,,...._.:_..,,'-._,,,,.-,..... , ,_ ,,,,
00000002-TSA14
somec_q" a drasttc Improvementtn wing performancecan beachieved. This s,bJect is Important enoughto constitute a
complotesectton (V) of this repop1_.
The velocityof thevehlclerelativeto the fluldU,,,. By
reciprocity tt is unimportant whether the vehtcle movesthrough
the fluid or the flutd streams past a stationary vehtcle,!
VP1oct ty_?.,Potent1al
The potential velocity distribution about a Shapecan be computed.byinviscid methods, the Neumannbeing currently
most popular° The shapeshould, however, be altered by adding
the displacement,thickness of the.boundary layer and probably
the wake. A newboundarylayer calculation can nowbe computedfrom the altered pressure distribution. This iteration becomes
increasingly important as the Reynoldsnumberdecreases. Where
the laminarbubbleattainssignificantsizeit wo_Idalsobe
importantto Includeitsgeometry.Recentlythe geometryof
the lamlnar.bubble(orat leastcertaintypes)has beendefined.
Velocity- Boundar_ La_e.r
The velocityin theboundarylayerU variesfromzeroat the
wallto U or the potentialvalueat theouteeedge. The exact
shapeof velocityvs.heightcurveis importantto laminar
boundarylayerstability.The concaveprofilesproducedby
strongfavorablepressuregradients(fiowacceleration) _!
promotinghightransitionlengthReynoldsnumbers.The linear
lowerprofilefoundin zeropressuregradienthasa muchlowe_
stabilitylimit,whilethe inflectedprofilesfoundin adverse
pressuregradientsare evenlower.
Viscosity- Absolute '_
Theviscosityor stickinessof thefluidp is theproportional
constantlinkingtheshearstressat thesurfaceto the rateOf
changeof velocitywlthdistancefromthesurface. It is
thereforein unitsof (pounJ)(second)/_ot2.
O0000002-TSB01
The ki.,omattc viscosity v t_ th_ ratto of the absolute flutd
viscosity to the fluid ma_s denstty. SIn(:_, the ratio appears
tn the Reynolds number, tt 'Is ¢oBvenlent t_ use v fop whichvalues arO available for air as a function of altt.tude tn the,
earth'satmosphereand for water os functionof temp¢_rature.i
The short discussionsgiven above are intendedto help the reader in
absorbingthe main text of this report. The phenomenainvolvedcan
be studiedin greaterdetailin the followingexcellentreferences:
I-1 - Schl-ichtingh Dr. Hermann - Boundary Layer Theory.
First published in German language under the title
"Grenzschicht-Theorie." 1951 McGraw-Hill BookCompany,
Inco 4th Edit;ion 1960,,
I-2 - White, Frank M. - ViscousFluid Flow McGraw-HillBook
Company, Inco- NewYork 1974 :,t
Although thts report concentrates most heavily on Reynolds numbers between
20,000 and 200,000 ttts belteved helpful to present this regime as a band
tn the larger range of Reynolds numbers between 1 and 1,000 m1111onso far
explored by man. Thts ts to show how the peculiarities of thts region are
a ]ogtcal fom of the beautiful and fascinating but ever-changing flow
phenomenaas one progresses through the "Realm ef Reynolds."
Toward thts end, the author bas prepared Figure I whtch presents an outltne
of the flow phenomenavariations, applications to motion tn nature, and
applications to man-madetransportation devtces as a function of Reynoldsnumber.
The lowest straight line provides the laminar flat r!ate frtctton coefft-
ciento The next line up extending from 105 to lOg provtdes the turbulent
flat plate friction coefficient. The remaining two ltnes are the drag
coefficients of spheres and cylinders converted from their normal frontal
area form to wetted area form to be comparable with the plate coefficients.
The marked decrease tn the drag of cy]tnders and spheres at a Reynolds
numberof 400,000 occurs when transition to a turbulent boundaw layer
proceeds ]aminar separattono A similar effect is seen for a 10% thtck
Gbtttngen 801 airfoil at o(= 12°,
The critical Reynolds number is about 70,000 and a hysteresis loop ts found.
In approaching the crttical condition from a lower Reynolds number, the
drag stays high to a greater Reynolds number than that to which the drag
stays low when backtng downfrom a higher Reynolds number.
Weshall now dtscuss twelve Reynolds numberbands from lowest to htghest
with brtef descriptions of the chang|ng flow regtmes and thetr significance
to atuPe's and man-madeattempts for efficient motion of solld bodtes
through fluids,
-7-
O0000002-TSB03
(A) VERY_LOW..RE,.Y__NO_L_DSNO_ER
At fractional Reynolds nulrbers, the flow is completely viscous.
Fortunately, even i, nature, wing destgn dooG not occur within
thts region. The practical consi-l_rattons on F.arth are the
falling rates of smoke_dust, fog and pollen particles. Thts
reoime is outside the range of interest of thts _ummary. For
further information see Hoerner, reference II-1.
(B) REYNOLDSNUMBERSBELOW150
This regimebecomesof interestin the d_ign ol turbulence
reducing screens II-3 and smokestreak producing wires II-4for low turbulence wind tunnelso It i_ desir:] that these
devices introduce a minimum disturbance to the flowo. For
Reynolds numbers less than 5 the flow is laminar and completely
unseparated. Between 5 and 40 a fixed vortex pair ls found just
behind ttle wire. For values between 40 and 150, the laminar
vortex street forms. In the case of smokewires, _ value of.
25 has been found to introduce negliglble disturbance to the
stream. The crtttcal RN at which screens produce troublesome
eddies var.tes from about 30 to 60 depending oa the screen
solidity°
(C) REYNOLDSNUMBERSBETWEENlO00 and lO,OOO
Here the flow is stronglylaminarand it is very difficultto
produceturbulentbouhdarylayersartificallyo Many insects
must fly in this regimeand naturehas arrivedat some unusual
solutions° The dragonflyhas :_saw tooth singlesurfaceairfoil°
It is speculatedthat eddies in the troughshelp keep the flow
m attached(II-5)o The conenonT_ousefly wing, when viewedunder
the microscope,has large numbersof fine hai:-likeelements
projecting normalto the surface_ It is speculatedthat these
promoteeddy-inducedenergy transferto preventseparation.Indoormodel airplanesof the microfilmtype operatein this
:-_. regime. Single surfacecurvedplateswhich have been found
to be superiorto flat platesor airfoilsare employed. It
has also been found that the blunt leadingand trailingedge
structurallyrequi_edactuallyenhancethe aerodynamlcper-
formancein this regime. _F_-
L_!I"_:,.._.......•. - .°.-_'--: ...... "" '-.', 5," •'_i "- '"' "....."._.:_i_.- :'_" .,', '_............."....... .
- mltt_m_f l "'I - ..____L,;( " " ..... _ " "_±'_' I
O0000002-TSB05
Bauer (ZI-7) has recently established in careful free fltght
testing that the total drag minusthe induceddrag of hand-launchedgltdor models, non.dtmenetonalizedon the basis of total
wetted area give a coefficient equal to the lamtnar plate value.It seemsthat we have had IOOZnatural laminar flow aircraft in .!
existence for sometimel The other stde of the coin is that these
aircraft can only operate at ltft coefftctonts of 0.5 or less,
Evenso, theirlift-to-dragratiosare the bestobtainableat
thisRNand theirsinkingspeedsare phenomenallylow {considering
the smellReynoldsnumber)due to theirverylowdragcoefficient
and in spiteof thesomewhatrestrictedliftcoefficient.Trim-
ming these models to higher lift coefficients producesa separated ,_laminarboundarylayerwithoutreattachment,lhe liftfalls,the i_
dragrisesby a verylargefactor,and theperformancemarkedly
deteriorates.To date,artificialtJ.ippingof the boundarylayer
has notbeensuccessfulin thisregime. Smallrubberband
poweredindoorscalemodelscalledPeanutscale(II-8)also
operatein thisregimebut theirperformancetechnologyis not
yet as highlydevelopedas the hand.launchedglidermodels.
(E) REYNOLDSNUMBERSBETWEEN.30,O00.AND 70mOO0
Thisregimeis of mostinterestto thetechnicallyo_ientedmodel
aircraftbuildersandflyers. Boththe NordicA-2,tow-line
launchedmodelsailplanesand theWakefieldrubberpoweredmodels
operateherein. Thesemodelsarejudgedon enduranceandmust
haveas highas possiblea ratioof (lift)3/2/dragoInduced
dragconsiderationscallfora highaspectratiowingbut this Im. reducesthe Reynoldsnumber,so greatcaremustbe takenin the
choiceof theairfoilsection-aspectratiocombinationemployed.
Sixpercentthickairfoilscan becomesuperCrlticalnearthe ii
'_ upperend of thisregimeand thecriticalRN can be decreased "
" towardthelowerend by artlficalboundarylayertripping. :4F :k,
:"_ Undernaturallaminarseparationconditions,thedistancefrom
separationto reattachmentcanbe expressedas
RNR - RNs_50,O00o Thus,in the lowerchordRN regimethereis simplyinsufficientdistanceto thetrailingedgefor
-lO-i!)
O0000002-TSB06
reattachmnt to occur, Nevertheless, excellent performing wtng
sections have.beendeveloped for this regime,
ThisRN regimebecamesuddenlyof nationalinterestin 1978v_en
JPL investigatedthepossibilityof exploringthe plane¢NaPsby
an aircraftflyingin the thlnMartianatmosphere(II-9),The
RN fellrightin thlsrange. It Is alsoof gnat interestfor
RPV aircraftoperatingat extremealtitude-m-lO0,O00feet(II-lO)
in the earth's atmosphere. To date, need for additional lowturbulence laboratory work in this regime has not been responded
to tn the U.S. but a few Europeanlaboratories havecontinuedtheir excellent earlter work.
(F) REYNOLDSNUMBERSBETWEEN70,000 AND200,000
At the lower end of this regime we find the bat in nature andi,
small radio controlled modelsailplanes andmodel powerplanes
as nlan-madedevices. Extensive laminar flow is easy to obtain
andairfOilperformanceimprovesmarkedlyin thisregime. At
the upperend.boundarylayertrippingdevicesare no lunger
neededfor sectionsas thickas 12%, Evena 1go6%thicksection .........
was madeto dellverreasonableperformanceat a Reynoldsnumber
of 150,000with theaidof a tripwire. Thereis a smalldata
baseforthisregimebutmorework is Justifiedin vlewof high
altitudeRPV and lowaltitudemini-RPVinterest.The laminar
separationbubble.isstilla significantpotentialperformance
robberin thisregionof flight. It shouldalsobe remembered
thatthepressurerecoveriespossibleforan attachedturbulent
boundarylayeraremuchlessat low Reynoldsnumberthanat high.
(G) REYNOLDSNUMBERSBETWEEN.200_000AND 700o000
In thisregimewe findman andnaturetogetherin f11ght, Large
soaringbirdsof quiteremarkableperformance,large radio
contrOlledmodelaircraft,footlaunchedultra-lightman-carrying
hanggliders,and thatsuperengineeringtriumph,thehumanpower
:, aircraft.
Again,extensivelaminarflowis easyto obtainand alrfoll
R performancecontinuesto rapidlyimprovecomparedto thatat
O0000002-TSB07
lowe_ Reynoldsnumbers, There is little worry over reattacbment
fatllng to occur after mid-chord laminar separation, but the
lamtnar separation bubble is still of' _tgntftcant Pelattve
length and doescost someperformance, Onemuststill beconservative in choice of the thickness-camber combination,
Very 11ttle gooddata extsts tn th'ls regtme,
(H) REYNOLDSNUMBERSBETWEEN, .700_000AND3.=.OOO,OOO
The aerodynamicdata in this regime is _.ery extensive ar,d of
vew high quali.tyo Twoearly NACAinvestigations havebeensupplementedby the excellent work at Stuttgart by Eppler,
WortmannandAlthaus,by Harsden_f Edmonton,by LtebeckofDouglasAircraft, and by Somersof NASA,
In the high performancen_zn-carrying sailplane we have mrked
performance improvementover the already highly refined _ IItypes throughextensive natural .laminar flow, TJlts 30-year
old technology is only nowbeginning to seep into the small ipoweredaircraft field. Large RPV'sdesigned for 55,000 foot
t
. _.............. altitudes also fall in this range of wing Reynoldsnumbers,
The laminar bubble can still cause a _ CD of about 0,001at a Reynoldsnumberof onemillion, but _ecomescompletelyunimportant for RN_ 4 X 106. At the upper end of this regime,
qutte large combinations of airfoil thickness and candlerape
permtssible together with far aft location of minimumppessupeo
(I) REYNOLDSN.UMBERSBETWEEN3,000:000 AND%00.0..¢000
There is a large data base from the WW11 era for this realm
of racing planes and general aviation craft, Very low drag
coefficients are possible through extensive natural laminar
flow but it is important to fly at higher altitudes to keepthe Reynoldsnumberper foot reasonably low, Constructional
andmaintenanceconsiderations ape becomingincpea_inglystringent, The laminar separation bubble at mid cl)t_rd is no
longer a problem, The turbulent boundarylayer on the aftpart of the wing can stay attached through very severe adverse
!. pressure gradients with the aid of modernairfoil design methods,L-"
= -
i. -12-
i _L- ' ,',., ," , , • _.._ ..... i, ii-f...... _ • i i ii i iN I
O0000002-TSB08
Various artificial boundary layer control schemesape effecttve
tn producingvery high maxlmumllft (II-11).
(J) R_YNOLD$_NUHBERSBETWEENg.,QOO,QOPAND 4pjOOO,pO_..O
It is still possible.to obtain extensive natural lamtnae flew tn
thts regime through strong favorable pressure gradtent@, for
example, on thick lamtnar atrfotls and on low fineness ratio
bodiesof revolution. This regime has very large payoff tnperformancefor 100%lamtnar flow surfaces whtchcan be achieved
through use of artificial boundarylayer stabtltzation...(for
example through distributed suction) (I[-12)o Suction ts
effective even tn strong adverse longitudinal pressure gradients
and in the. presenceof transverse pressure gradient inducedcross
flow instability causedby wtn9 sweep° Net drag including the costof sucttoo can be reducedto about 1/8 that of turbulent boundary
layer wings, Data base is appreciableo Small torpedoesanddolphins also operate in this regime (II-13)o
(K) REYNOLDS,NUHBERSBETWEEN40tOOO,OOOANDlOg
Vehicles in this regime include large fast aircraft andsmall to
moderatestze submarines, Boundarylayer flow iS mostly turbulent°
In nature, whales also operate in this regime, Little laboratorydata is available to date, The newcryogenic tu_el at NASA '(Langley should provide data in the future,
(L) REYNOLDSNUHBERSGREATERTHAN10g
Large nuclear submarinesoperate at these extremevalues, The
drag is. primarily turbulent fraction drag, There is great interesttoday in finding practical ways to reduce the high Reynoldsnumber
turbulent friction drag in a practical mannerapplicable toextendedcruising duration.
i-
"13--
m _ __• L. " "Gsb ,., .. • ....... -- -
O0000002-TSB09
FLOVIPHENOMENABIBLIOGRAPHY
II-I Hoorner,SlghardF. - F)_u!dD_namlcD.rag- Publishedby the
author,14B BusteodDrlvo,MidlandPark,Now Jersey0743_ 1965
II-2 Hoerner,SlghardF. and Borst,HenryV, -Flu:i_d_.p_ynamlcLif._.-
Publlshedby theauthors,P.O.Box 342,Brlckto_.m,N,J, 0B723
1970
II-3 Schubauer,GoB. and Spangenberg, G. - "Aerodynamic
Characteristics of DampingScreens" NASATN2001 January 1950II-4 Batell So M. andMueller, T, J, - "Visualization of the Laminar-
Turbulent Transition tn.the Flow Over an Airfoil Using the
Smoke-WireTechnique" AIAA Raper 80.0421 to be presented at1;..+.hAerodynamicTesttng Conference- Colorado Springs,.ColoradoMarch18-?0,1980
II-5 Hertel,Helnrlch- Structure-Form-Movement- ReinholdPublishing
Corporation,NewYork 1966
11-6 Shapiro,AsherH. - Shapeand Flow The FluidDynamicsof Drag-Doubleday& Company,Inc.,GardenCity,NewYork 1961
11-7 Bauer,AndrewB. - "TheLaminarAirfoilProblem"NationalFree
FlightSocietySymposiumReport 1975
II-8 Hannah,Bill- PeanutPower- HistoricalAviationAlbum '_
Publication- TempleCity,California1980 lII-9 Seaman,DroGeraldR. - "A ConceptStudyof RemotelyPiloted
VehicleforMarsExploration"FinalTechnicalReportunder i
Jet PropulsionLaboratoryContract955012 Augustl, 1978
II-lO Carmichael,B. Ho - Applicationof Sailplaneand Low-Drag
UnderwaterVehicleTechnologyto the Long-EnduranceDrone
Problem"AIAA/MIT/SSA2nd InternationalSympoisumon the
TechnologyandScienceof Low Speedand MotorlessFlight.
Cambridge,Mass. SeptemberIf-13,1974
II-ll Lachmann,Dr° G. V. - Bounda.r._Layerand FlowControl- Vo].I
PergamonPress NewYork 1961
II-12 tachmann,Dr.G. V. - BoundaryLayerand FlowC_ntrol- Vol.II
PergamonPress New York 1961
_ ]{I-13 Carmichael,B. H. - "UnderwaterVehicleDragRe._uctlonThrough
: Choiceof Shape" AIAAPaperNo. 66-657- Presentedat Colorado
.:; Springs,ColoradoJune13-17,1966
-14-l
O0000002-T,SBIO
Fluid flo_ sQparatienon man-madedevices ha_ beenone of the most
dangerousand perslsten_;phnnemenain the 1_nghl_toryaf flulddynamlcB,
The deetructlvodynamicresponseof hlun_devices,l.e,,powertrans-
mission 11ne_,suspensionbridgecables,and towingcablesfor underwater
devicesmark oneend of theproblem, The stalllngof aircraftwingsha_
Instlga%edcomprehensive_tudyIn thisfieldfora_ leasta half'century.
Theattemptsto providere._sonablygoodperformanceformodelaircraft
andhighalt(tudemannedalrcraftare oftenaidedby observationof
nature'selegantsolutionsfoundon smallto mediumsizedflyersin the
insectand birdworld,
The literatureis so extensivethatthisreportcanonlyCoverthose
referencesreadilyavailableto theauthor. Theextensivebibliographies
in the referencesquotedheremay be usedto delvefurther,It is
inevi'Cablethatsomeverybasicand helpfulstudieshavebeenoverlooked
due to theshortdeliverytimefor thisreport,
The phenomenaof laminarseparationon liftingairfoilshasa fm_damental
influenceon theaerodynamicforcesand moments.Evenat veryhigh
Reynoldsnumbcrs,leadingedge laminarseparationcan havea decisive
influenceon the stallingbehaviorof aircraftwings.
At chordReynoldsnumbersbelow50,000,laminarseparationwlthout
reat_achmentcan leadto largelossesin liftand dramaticincreases
in drag, It is possibleto deslynthinairfoils,e.g.,t/c_6% of
quitegoodperformanceat chordReynoldsnumbersdown to 30,000. Use
of artificialboundarylayert_'ippingby variousmethods(ascovered
in SectionV of thisreport)can improvetheperformanceof thicker
airfoilsin thisnormallysubcriticalrange. _t Reynoldsnumbers
between700,000and 1,500,000,theboundarylayercanbe convertedto
theturbulentformmoreelegantlythroughuseof the shallowmld chord
adversepressuregradient(calledinstabilitygradient),Thistechnique
is widelyused to improvetheperformanceof laminarairfoilsforman-
_. carry'ingsellplanes. At Reynoldsabove4,000,000,thistechniqueIs nolongerrequiredandwouldleadto a lossin cruisingperformanceif
employed.
-15-
#
iI •, r'l ...........: , ,,"i__" "_E. ""'_s...............
Studtes of lamtnar separation wtth re_ttachment prtor tQ the tratltng
edge [the so-called laminar separatlQn bubble) have been vigorouslypursuedfor the last feur decade_, It 'i_ nowposstble t_ define the
bubble geometryand tt_ Influence on airfoil perfQrmancn,
CHRONOLOGYPRINCIPALINVESTIGATOR5AND_JOR STEPSIN UNDERSTANDING
|
1Year Investigator Contribution Rof
1904 Prandtl DiscQveryof theBoundaryLayer III_1
1914 Prandtl Effectof BoundaryLayerTransition III-2Relatlveto Dragof BluffBodies
1933 M1111kanand K1eln Effectof b.l.trans,relativeto III-3separationpointon airfoilmaximum11ftcoefficient
1934 .Melvi11-Jones Described3 typesof stall. TurbulentIII-4b.1.sep.a; i.e.,leadingedgesoo.withoutreattachment,leadingedgeseparationwithreattachment
1934 von Kamanand DiscoveredR_sep,/_'s'7"anT.is IIl-5Millikan constantfora prescribedpressure
distribution
1938 vonDoenhoff DiscoveredR sep to R trans= 50,000 III-6R sap to R turb,reattach.= 70,000
194U Schmitz Airfoilbehaviorin criticalRN range Ill-721,000tO 168,000.Importanceofstreamturbulence,artificialb.1.tripping,choiceof t/c,f/c,leadingedgeradius
1940 Pfenninger 6% and 9% t/c extensivelylaminar III-8-43 airfoilsat RN betweenI00,000and
760,000. Improvementswithsurfacestepsandwavesa"da_r_cs
1948 MaekawaandAtsumi Separationand transitionstudyon III-9bentnlateR septo R trans= 25,000
if R6sep>1200.ReattachmentfailswhenR lengthis too large
1951 Bursnalland Loftin Foundmid chordlaminarbubbleat III-lOlow_ on thicklaminarairfoil
1951 McCulloughand Gault Defined: (I)stallpreceededby III-llturb,b.l.sep movingforwardfromt.e.forthickairfoils,(2)laminarleadingedgeseparationwithoutreattachmenL(3)"Lamlnarl.e.sepwithreattachmentwhichmovesaft as _ n:Fnc'reases--thlnairfoilstall-16-
O0000002-TSB12
Year Inve_tlgatQr contrlbutlon Reft
IgSB McCulloI_gh F(_und0006 airfoilreattach_'fQr all 111,.12RN of 1,5 x 10t__ 6x10_00Q7 alrfollnot ro_tt_chodforRN :- 6xlOt;00Q7.5 + OQOB alrfQilnot r_attachedforRN ; _xlO('
II)@@ _ault _tudlod I,_.,_p on O01O and 6(31_ OIFI_ III-13t._. _op. otl 5C_ - O1B,
FoundR_*_op _',_no_a_,aX sopw_0.75 ,_0.55,_lam deer by arab.turb a,d Incr RN,Convorcjenceanglo o a_ f(RN),
195fi Norburyand CrabtrOB Mathematlcalpredictionof pressure 111-1.4distributionon airfoilwith a longbubble
1958 Chapman,Kuehn, Subsonicand Supersonic. 400 ,'R_ < Ill-15Larson 5,000,000
(I) Transitiondownstream ofreattachment(2) Trans. betweens_:p4ratlonandreattachment(3) Transitionprior to separation
19_r9 Moore Experii:lentwith steppedplate-l(_w Ill-16press, gradientFor R,s*< 500 laminarreattachment,Fnr R_* , 500 turb reattach- pressurecoefflcientis independentof RN_bubble length= I/RN,For R_* < 500 long bubble-largeeffecton pressure,For R_* > 500 short bubble- no largeeffect on pressu,'e,
Long bubb!e length= f (shapeand _)byenot RN,_ _ihort_bubble burststo
long when {cD_ >00"5c"l)/(l'cpl)> 0.36eve_ when R__
1959 Burrowsand Newman Suctionwithin separationregion 111-17 <reducespressureat forwardend ofbubble and increasesthe pressure :_recoverycoefficient. Size of bubbleand b,l. thicknessdownstreamarereducedby b.l. suction
1964 Tani Confirmedbubble formswhen R.* > III-I8criticaland pressurerecove_
coefficient< critical,R_* criticaldifferentfor cylinders_nd airfoils.Criticalpressurerecoverycoefficientnot unlversal,
-17-
O0000002-TSB13
Year Investigator ContributiOn R_f
1964 Morkovln Separation flow pattern._ behind a III-19cyltnder over complete Reyltoldsnul_..,,urrange, Hnl_xp_cted increaso
0_in drag at Rd .1 . Data ono_cillatoryTift a_ f(RN)
I@67 Roshko Di_c,_so,_the Iimltationsin present III-20theory to dof'Ineseparatedflow_
III-211969 Ga_ter °s . aUl _,f esi/s at bursting
L short bubble lennthlos = const_.n_/(gs
R_ = 64,000sep to reatt_ch_nto 40,000-_50_000 sep. to transition
1972 A,G.A.R,D. Many fine paper_on high lift systOms...III-22, and aircraftsc,l_li_,,
1972 Lalne NavierJ_toXes_,luationsof laminar III-23boundaryseparatlonover step inflat plate
1972 r_obbtnga_van Ingen Defines annle of the senar_tion stream- III-24and K_oi line Tany = - 3 dtoldX/_pl_x=
K/Re sep. Uefi)lespres_drecoefficientat reattachnent
1975 van Ingen Definesbubble geometry,bursting, III-25pressuredistribution--cor_latedwithex_erlment. See figureswhich follow.
1977 van Ingen DefinesX trans.- X sep. as function III-26of osep._Rosep, and turbulencelevel.Corelatfonwith experiments. See figures
1977 Young ReviewsknowledqP._n unswept, and III-27laminarseparationbubble-'s_.gures
1978 Mueller Flow visualizationdeternlined: III-28separationpt. transitionpt._ andreattachmentpt. on airfoilleadingedge for 150,000<RN<420,O00
1980 Batilland Mueller Detailedprofileand platformviews III-29of laminarseparationand transitionby smoke-wiretechniqueon 663-018airfoilat 50_O00<RN<130,000
IgSO Venkateswarluand Finitedifferenceb.l. analysis III-30Marsden togetherwith some experimentally
determlned constants,define locationand geometryof separationbubbleat60% to 70% chord on laminarairfoilat 500,O00<RN<3,000,O00.Predictspressuredistributionand b.l. velocityprofilesdownstreamof reattachment-18-
i.t!_x..",..,< '-'" _/,-...........
.... O0000002-TSBI'I
--.,.,_.>........._--_,_.,,:,_._._:_:_:_ _,_:._vlf____-_- ;_",,:: _- . T_._,_.......,,y,
F
F!,
_ Discussion
ii_ The formulation of the boundary layer concept by Prandtl in 1904 solved "the long-standing ,_stery concerning the differences tn o_served Elutd
behavior and the tnvtsctd flow theory, By 1914, Prandtl was able to
_/ explain the large drag differences observed by different investigators
for blunt objects such as spheres and cylinders on the basis of the
condition of the boundary layer prior to the flow separation location.
This effectwas appliedto thc stallingof airfoilsby Millikanand
Klein in 1933.
In the WrightBrothersMemorialLectureby Melvill-Jonesin 1934, three
oistirtcttypes of wing stall were described. The thick airfoilgentle
stall in which turbulentflow separationgraduallymoves forwardfrom
the trailingedge, laminarflow separationfrom the leadingedge without
reattachment,and laminarleadingedge flow separationwith flow
reattachmentto the airfoilsurfacedownstreamof separation.
In 1938, yon Doenhoffaccuratelydescribedthe laminarseparationbubble
in an adversepressuregradientand found by experimentthat the distance
from the separationpoin_to the transitionpoint along the separated
streamlinecan be definedas R transition- R separation_ 50,000and
the total bubblelengthas R reattachment- R separation_ 70,000.
In Ig40, Schmitzpublishedhis classicalwork on low Reynoldsnumber
airfoilexperimentsin a low turbulencewind tunnelat G6ettingen.
He clearlypointedout the influenceof stream turbulence,and artificial
boundarylayer trippingin extendingg_od airfoilperformanceto lower
Reynoldsnumbers, liealso recommendedoptimumvaluesof airfoilthick-
ness, camber,and leadingedge radiusas a functionof Reynoldsnumber
for flight in the low turbulencefree atmosphere.
At about the same time, Pfenningerwas exploringthe limitsof airfoil
drag reductionthroughextensivelaminarflow in a low turbulencewind
tunnelat Zu¢_ch. He found that the perForn_nceof 6% and g% thick
propellerairfoil_ectionscould be improvedby boundarylayer tripping
using air jets normalto surface,large surfacewaviness,and backward
facingsteps in the surface.
-!9-
F .. 00000002-TSC01
Thwart:now t'ollowed |ntcnsJw invt:stJgatJ_n,_ _f fluw _paration, lamtnar
LTuhl_l_s,alul airfoil _t,alling b_;havl_,', In 1_, Mat,k_Wa and AtsulltJ
ill Tokyo d lsc_wred their flow t"t:,ltt_tchm_:nt did m_t t_c_:ur wtm_l the
bubble le.n.qthRtWIlold._llUiIIb_.rexceededa rrii.it:,llwllue of about
75,0Iltl,In i.ht._early to toldI95tls,McCullnugl|_md Gault wt:reable
t(} define the t,hrem type_ of airfoil stall first noted by Nelvill-
Jones in flre_i: detail t_ t,eMIIS(_f the pertin+:nt: boundary layt:r papa-
meters,l'heyfound that I{_*at st_,paratlonhad l,oexceed 500 forreattac_mlentto occur In sI_'oll;l_dversepressuregradi¢mts, They
found the laminarlenqthin the _eparationbtlhbleto be 75% to 85%
of tl_etotal bullblelengthand definedthe angle of closureof the
flowwith the surfaceafter transitionas a functionof Reynolds
!iiIn 1959,Moore found that when Rs*at separationwas less than 500,
a 19]t9.laminarbubble fo_nedwith very largeeffectson the pressure
distribution,but thatwhen R_*sep exceeded500 a short bubble
formedwith only small local effecton the pressuredistribution. :'I
They also found that even when R_*sep.exceeded500 and a short bubble Ji
initiallyfor_d, that it could burst to the long bubble type when the ._
angle of att_u'kwas increasedand the requiredpressurerecovery
followingsep,_ratlonexceededa value of
o _:(Cp recovery" Cp sep.)/(l.Cp sep.):0.,_6
In an extensiw_,sunm_aryin Iq64,Tani pointedout that R_* criticalat
separationand the criticalpressurerecow:ry,.,seemed t.obe different
for cylinders,_nd,_irfoils.
In I_)69,Gaster furtherdefinedthe conditionsunder which short bubbles _!
.._ couId burst itltolong bubblesas -_,'(_s"hCAllll''c.ritlcalas a functiollof R0 '_iat separation.
From the e,orly l_)70sto tlm presenttin_,,VilliIngenand his colleaguesat,
llelftUniversityin the Netherlandsand Young and hi._colleaguesat the
Universityof [.t)ndot_hay(_.nl,ldeimpre._iw,._trid..,,_in correlatimlvarious
IlN:thods of COlllplltJng the fluw '..;=)par,ltitm, bul_lq_, I_ehavior, and resul ttn!l
twes._ure distributions with carel'u'lly cont_'oll¢,d _,×periments. Presentlyo1 Venkat.esworlu ,rod Marsd(m haw, apl)lt_,d p¢_werful Finite dil"ference
calcul_iti_mst(_ tim IW',flq¢'mwith _,t_c_)|tr,lgin!lm,,_ulI:_. Muell=_r and his
O0000002-TSC02
colleagues at Notre Dameare continuing the excellent flow visualization
work begun by the late F.N.M, Brown In wind tunnels of very low turbu=
lance level providing excellent detatls on separate boundary layer
tran_Itlonand reattachmentat chord Reynoldsnumbersof BO,O00 to
420,000. The clearestphotographsof flow separationfrom both blunt
objectssuch as spheres,and on alrfoilsat angle of attackmay be
found in F.N.M.Brown'sremarkablebook, See The W_nd B1o_._..ww,ref. III-3?.
The text is also one of the n_st i11uminatingto be found in the long
historyof fluld dynamics.
It must be emphasizedthat it is still necessaryto proceedin a semi-
empiricalmanner in predictingseparationfor a new case, and inevltably
there are disappointmentsjust when one feels that thingsare well
enoughdefinedfor engineeringpurposes. In 1972, Laine at the University
of Helsinkisolved the NavierStokesequationsfor the separatedflow
from a rqarwardfacingstep on a flat plate. Thompsonof MiSsissippi
State University,referenceIII-31,is presentlyattemptingto correlate
similarexact solutionswith the experimentalwork of Muellerat Notre
Dame. The computerrequirementsare formidablebut such calculatlons
shouldeventuallyproviderealisticresultsfor even the most complex
flow separationproblems.
CalculatingFlow BehaviorInvolvingLaminarSeparation
It is desiredto calculate:
I. The locationof laminarseparation.
2. The angle of the separationstreamlinewith the surface. I
3. The lengthalong the separationstreamlineto transition.
4. The angle of closureof the separatedboundarylayerwith
the surfacefollowit_gtransition.
5. The locationof reattachmentwith the surface.
6. The lengthof run after reattachmentrequiredfor the
boundarylayer velocityprofileto returnto normal.
7. The criteriafor which reattachmentdoes not occur.
8. The effectof the foregoingon the pressuredistribution.
g. The effectof the separationbubble on boundarylayer velocityprofiles.
lO. The penaltiesin drag, lift, and moment _or those cases where
reattachmentdoes occur.
d
-21-
00000002-TSC03
The separation bubble geom_.try as outlined above ls sllown in Flgure III-1,from the tnittal yon Doenhoff concept of 193H through several intermediate
experimenters and concluding wtth the detatled 19_ description of
Vonkatesworlu and Marsden sht_wnin Figgv'o III-2.
1. The lOcatton of laminar separation is shown In the upper plol; of
Figure111-3 in terms of tlleboundarylayer shape parameter
H_ep = 3 + O.0713/msep as a functionof m _ - o. dUT-" _" Theintersectionof the laminarboundarylayer H historywith tile
criti¢:alvalue gives the desiredlocation. Some typicalvalue_
of R_* at separationfound on spheresand cylindersas afunctionof Reynoldsnumber based on diameterare shown in the
middle figure. Valuesof R_* at separationfound for variousairfoil,angle of attack,chord RN combinationsare shown in ....
the lower figure.
2. The tangentof the angle of the separationstreamlinewith
the surfacetan y is shown as a functionof R¢)at separation
on a logarithmicplot, upper figure 111-4and in cartesian
form in lower figure III-4. The scatteris small and the
definitionquite good for objectsas diverseas cylinders,
flat plates,and airfoils. Correlationwith smoke line flow
visualizationon a Wortmannairfoilfigure III-5 is seen to
be excellent.
-" 3. von I)oenhofffound during his low turbulenceplate measurements
under adversepressuregradientsthat the Reynoldsnumber
(basedon local potentialflow velocityand the length from
separationto transition)was about 50,000. Some recent
measurementson a Wortmannairfoilgive valueswhich range
w from 37,000at ROsep = 175 to 70,000at R%e p = 415. FigureIll-6. The valuesfound for bubbleson swept wings vary from
)T) 42,000 to about 60,000,while those found on a cylinderwere
much higherthan those found on airfoils.
_ An excellentcorrelationIs providedby van Ingen in the form
|04/R%ep. vs. A,/Osep_ROsep.with an assistingvariableinthe form of ambientturbulencelevel expressedas a _.of stream
velocity. The experimentalvalues fell on predictioncurves
obtainedby integratingthe amplificationof snBll disturbances
"eLL.-
•.'_i, , . . . _ ,,,_ ,. ....._ ,,,_ ,__,,_,,__%_.. , "......._ "_i
00000002-T$C04
to ratioswhich varywith the ambientturbulencelevel,
The resultsappear here as figure Ill-7,
4. yon DoQnhoffin his originalconceptof the laminarbubble
suggesteda closureangle of 15° from the separationstream-
ltne based on the typtcal spreading angle of the turbulence.Maekawaand Atsuml found a value of 17° to fit betterwith
their observationson separationover a sharplybent plate,
Gault found in his study of the NACA 0010 and 663-018
airfoilsover a range of anglesof attack of 4° to 15°
and chord Reynoldsnumbersbetween2XI06 and 6XI06 that
the closureangle varied from 15° at high Reynoldsnumber
to as high as 52° at low RN. These valueswere based on
the assumptionthat the separationstreamlineleft tangent
to the surfaceand laterwork has Shown this assumption !!to be incorrect,
5. A constantbubble lengthReynoldsnumber (basedon the
potentialflow velocityand distancefrom separation ]
to reattachment)of 70,000was suggestedby yon Doenhoff.
Experimentalvaluesfor the 0006 airfoilare 48,000+59,000.
For the 0009 airfoil72,000+79,000,and for the 66018
airfoil62,000+]14,000.The value for mid chord bubbles
on thick airfoilsare 120,000to 240,000. See figure III-8.
6. The distancerequiredfor the reattachedboundarylayer to
recoverto a normalturbulentform followingthe bubblewas
first noted in the excellentsummarypaperof Young as beingm
equal to 100esep.for the case of unsweptwings, I00 to 150esep.
for a 26.5° swept wing and 150 to 300esep.for a 45° swept wing.
i 7. The point of most practicalinterestto the strugglingapplled
-_ aerodynamistwho must predictstallingbehavioris to define
when a short bubble (whichhas rather limltedeffectson, pressuredistributionand thereforeon lift, drag, and
," pitchingmoment)w111 burst to the long bubbleform. The
first conditionis that R_* at separationmust exceed500
if a short bubble is to form. For lower values,the bubble
is long and in many cases reattachmentis not possible, Even
-23-
'_i._;. ..................................... _,.,,. ., V , ......... 1
""' 00000002-TS005
when ROsep exceeds 500, the resulting short bubble willeventually burst to the long bubble type when angle of
att(ickis increasedsufficiently, In IgBg, Moore in his
experimentson a steppedflat plate found that this {iccurred
when the differencebetweenthe pressurecoefficientat
reattachmentand the pressurecoefficientat separation
dividedby (I - the pressurecoefficientat separation)
exceededa value of 0.36. (Cpreattachment . Cp sep)> 0.36.
See figureIII-9-A. In 1969 Gasterput it in termsof the
adversegradient(whichis nearlyalways linear)for the
same regionbetweenseparationand reattachment.
t)s . A_.L = a Functionof Rosep' Son_ experimentalAx
resultsof non-burstlngbubblesobtainedin tests Of a
Wortmannairfoilare c_nparedwith Gasters limitingline
in figureIII-9-Bfor valuesof ROsep less than 500.The _ value for burstingare given for McGregor'sairfoil
at three anglesof attackfor chord RN between0.7 X I06
and 2.7 X lO6 in figureIII-9-Cand for a Piercyairfoil
at Rc = 1.7 X I06 in figure III-9-D. The More criteria
of%r_t = 0.36 seems to be adequate.
8. Pressuredistributionson wings at very high Reynoldsnumbers
in the absenceof flow separationcan be accuratelypredicted
by inviscidflow calculations. At lower Reynoldsnumbers,in the
absenceof flow separatio_a more accuratepredictioncan be
made by adding the boundarylayer displacementthicknessto the
wing profileand re-computingthe pressuredistributionfor this
combinedshape.N
A short laminarseparationbubblewill cause a local flattening
of the pressuregradientin the regionof the laminarportionof the bubble,followedby a steep pressuregradientin the
:_ turbulentbubble region. At reattachmentthe pressure i
! recoversto the same value presentin the absenceof the short
I bubble. -24-
i!r" •
00000002-TSC06
A long bubble causes very large changes in the pressure distri-
bution, The negative pressure peak ahead of the bubble is
greatly diminished as is the ltft. Figure III-lO-C clearly
shows the difference between long and short bubbles. Figure
III-IO-A shows the difference in the pressure distribution on
a cyltnder wtth transition preceedtn9 and following separation.
Figure III-IO-B shows the pressure distribution chal)ge on a
thick atrfotl as One proceeds from a moderate Reynolds number
with a short bubble to a lower Reynolds numberwith a long
separation bubble which does not reattach. Figure III-IO-D
provides pressure distributions for a 45° swept wing with
short separation bubble along the complete span, E shows short
bubble inboard and long bubble outboard, and F shows leng
bubble along the complete span.
Computation of the pressure distribution under lOng bubbles
with either reattachment or non-reattachment is probably
academic since one wishes to design to avoid this condition.
Under a short bubblej a good engineering approximation can
often be obtained by using the data on Separation point,
angle of the separation streamline, length to transition,
clostng angleo and total bubble length previously presented
to define the geometry of the bubble. Then assumean almostt
constant pressure value from separation to transition equal
to the separation value, Next draw a linear pressure rise
from transition to the reattachment point where the reattach-
ment pressure is equal to the value with bubble absent,
A more exact solution may be found in reference III-30 andwtll be discussed at the end of this section,
i
9, Detailed measurementsof the distorted boundary layer veloctty
profiles within short and long bubbles on a 45° swept wing in
both chordwtse and spanwtse direction are shown in figure III-1].
Correlation of measured with predicted chordwtse boundary layee
veloctty profiles for a mid chord bubble on a thick atrfotl
wt11 be presented in a following section.
-25-
_e_,• "
00000002-TSC07
10. For the case of short bubbles with reattached flow the
pressure distribution is not altered enough to mrkedly
affect ltft and movement. For leadtng edge short bubbles
one often finds a change of 11ft curve slope and moment
slope at the angle of attack where the bubble forms. The
small changes whtch do occur could be accounted for by
integrating the slightly altered pressure distribution,Short bubbles cause a small but measureable tncrease tn
drag which has been found by Marsden to be about
ACDo= 0.001 at Rc = 1X 106 for mtd chord bubble on thtcklamtnar airfoils°
A Cpmpartson of Experj,nen,t With the _st Cpmplete SeparationBubble Calculations to Date
Reference III-30 by Venkatesworlu and Marsden is certainly the culmination
of the long efforL to understand and predict lamtnar separation bubbles.
The reader will have noted a great deal of experimentally guided emptri-
cism in most of the foregoing discussion. Reference III-30 reduces this
to a minimum and uses finite difference calculations to provide an improved
theoretical prediction. The case covered is the mid chord laminar
separation bubble on a thick laminar NACA663-018 atrfoil Comparison
of theoretical predictions were madewith experiments at Rc = 0.8 X 106,= 2°, and a turbulence level of 0,02% at Edmonton, and with experiments
at Rc = 1.7 X 106, _ = 0°, and a turbulence level 0.2) from the NACAmeasurementsof reference III-lO. The schematic diagram of the bubble
is given in figure III-2. The total length of separation (figure III-12)
comparedwtth three experiments can be expressed as Lb = 75/Res. The
corresponding bubble height at transition (figure III-13) is expressedht 4.8 X 106
by _-"_= U _/_ Re 2 The excellent agreement of computed b.1,
proftles wtth those measured at Edmonton is shown in figure III-14,
including the region downstream of reattachmen_, This is most important
for the calculation of the drag.with a bubble present. Excellent agreement
is found tn figure III-15 between the predicted and experimental pressure
)
00000002-TSC08
distribution. The history of the boundarylayer shape parameter H is
given in ftgure III-16. Comparisonsof predicted and experimental
(reference III-10) boundarylayer profiles Including the Pegton
following reattachment ape shownin figure III-17. This fine studyreference III-30 presently available only from the University of Alberta
has been submitted fop publication to the Royal Aeronautical Society II
of the United KingdOm,
00000002-TSC09
• I' ........1r¸'", ! ......... "_I
" _V F'("_I_QtlAt,ll"_
(_retlQn Bubble :_ a i'o¢hmont Horbur#tlnclCrnbtreQ'sslrnp'.d]cdmodel er flclW plltlem whh a bubble, <
YonDo_nhulT's¢onwptN'bubbleformnllon,
l ......i°" il -,.io._.......,,.- _-_!....I........I..................................... till' # "I - PRI_SSUIIE
0.1 ,-14l, f X_Ii,t',OISTtlI_U_N
llil,l \d....-"]lui,l_/IJIJl+" I1 III It,_ i .....
,<<,,,..... < ,>".;<<,.,,._,',o';__,v_ _, ' I __7-L.... L%.. ]• "_ '_ # " I _-f " , "r ' Iti_tll AI ,iLl, IIN/I..-" ,,_",..-,-_' • T ,,,^_,,o_', -- _._L.
,,..,- \ . °*-S, ] i°.,..., C '5 ' LIY, IIhI'.N' ". IN,
• ' ' _" IILVIiISI rir, w vulitt_, *0'0_ LI
I I'.li dill', lilllill It Ill I1| I IhUli if '_lll,il _Itlllll I',,I,Id.' Ill ,t t,i _,i.il;') . "0'1
I
°'_1-" 1-.77--il _'_.u_TlI=l .Itl .....;!'--I"/"."-I'ilu_lul._._;T,.t_._,i>
oi I ";?._ _il ,11
s r'_ . ol_._.l..... __':i_.'_t__!_rz/__.A", _.',";_ _'," '_'i', v _ I ' I -iO • r_+ 140I ..i_-l@ I III,
', ....... l: ..... l',,_ " (' ; ' I __',l _f_i._ I.i.._,,,,,'7' It I MoTTL£O I_ATrERN......-.,......... .-.,,.y,.._-_ •
..f : ;, -,,. ,, ' _,_, 1
LA !rlPIII_D,CX PATTERN
%1..... .... _. __./ i I "Le iI rl,l 1,1,1e i "=l " • I "
,%' ',li/rl', ,,i I'U.I'I 151t.AUY_.ll,!_KE,,'" I J E:ANU
7-."?,'-_'zr,.-. ' -_ Iv/I:: r-._,, t rt III1ULI_NT _FFU_ OM
h) SI:_t'I."l oF li,'l,,k_' I'h",' l;I,,._,'In[l lho "",',',I"_. lt,AIIIIIXtIOWNSTNIrAM:.' :," ; I/,_,,pArtlLY UPSTNEAt,t
li' 'tl',"',ll I'llll 't'li l_il' (R' ',Jill I !11 _': ..,,.I.. (/_/ % ,'ll,lll!;ll i_"11 '1' t ;ill,l _lll' l,"',itl Iqii _'1_ 1!4 .... .,./Ol_l.-.-,-.,.:.-._.,,..#.-i,,# r...#,..l,..i._.i.._
' *- .M.!(IKI Etllttf I
-_._ t PPF' AFIANCI;O_:SMOHE
J.. :, TI,, :;,'l,_ii ,'_ l,m II,lhhl, 1 l',l,i ,_i,i,,.t 'l lie .%ti'tlt'tlile _.,Ii.i bilt_i,le tlhl_ln, ted lly tl',c l'hiw ov,:i"Ll' _,'i,,il.ll 1, ,_1tt l_ I::ll,'rh.. ill 'i. _1Ilcp, ,_l_.'p hvltthl ,{I131; in. l)i.t,ii,cc sit' lth'p frt_l-ii ll_allilit:
c¢l}.,v 6'.'t ili, Ul_' .51_ft./_"¢. /_I'" 6...0,
iL FIGUREIIl-I LAMINARBUBBLEGEOMETRY
-2B-
!.
_':.-_• .4
O0000002-TSCIO
__ T'_ : .̧........... +.- .. ,...._..-._,--_ ...................
r ........ ,+.m...._:....l--{- -4,_,,....... .'.,,L._ '_
........... _,_ .....L-I_. b,
............. _ ....._i_,-i F_;
...... 3Or ........
..... 211 _ ,v+._+
ll(m+ for hlm, _I,,'+'I,,I v,,I, I. " /
hoh=lhm' of lh,' bO.l.l,.p --. / " '22 ....la).r +'q. _ lon_, '+" ,
----I,ffl
F-
4000 I * " ClrCt+'_r ¢yl;;,'_'= Clrculor cyllnder43• v ¢trcu;or cyitndor3 • /J d. [_.4cm I
, e rJltpfic cyl_n_e'_'s_ '_ _ d • I G.4 cm (wllhwlro) I=: * o _phore'_ • o d e31*7 ¢_ ___._.._._ '
;++?o
" I_.,.' "._ .!. ! ....
!....i:: -il('._O'B t _ 4 I 2 ,_ 6 6 to
IO-_R 10"sR
CaK'ulatcdbounda_'-laycrReynolds number _t ._paratlon on clrculoZ
c)iindcr,e_.lipticc)iindcrand sphere.
_., t.! v-:.-' ,y+r :,,.:yncL",' Nt,.'-1+.+: :,+t_,:'.a.";,do_
[]- tT.vpoof RcfcrCnca
G _ `'C '+) it= ....
J'8 ".lO+ $';" ,_93 i 0'22 ShOrt |8,224'_'_ i hmg9'0'
(_1.\_,:,', 5.S x t? _ 4<? .(10 j I 22 sltert 19,22
_06 2._,::10s _.0° 5"0 29 ._h_,rt 28b.5° 350 IcP._
4.6'<lOs 6'50 071 0.24 short 2S
?.0 "_ 392 long 286'8'.:I0 _ (_.0' 774 0.21 sho,'_
O<Y,_8 2 0 '.'I0" S.O: 5)2 0 27 .,h,,:t8._o 3._2 lor_
4.0 " lO_ 9'0+ 812 0'24 s:',,+rt 2_tO,U_ 42_ l_,_
FIGURE III'3 LAMINAR SEPARATION PREDICTIOll_3o-
00000002-TSC12
OtillIINAI,,PAGEl_lOF POOR QUALITY
I','.'/
!' _ \. v l_i_ fl:_t f ,',_J ;,*_f.'.,,o401"I r \ \ t_ (t',l 7lift,,,1d','.4cdhnd?f
t .Cl",:j L _,_ '_. , (I.) /_{flll'm d'a _Jl.ifldao|',.'1;,_) -',_.\ I {i4 I._rt,t I.y,v,,l:]01rr,'l
: 0,4{} _.,p, fii._ '_',,.t_,l))" _LI_'%. n If)" '._t,c_rifl..t| l'lal,_
,} ,, %
{it0 , (!!_),,,P _\,l,
Ou"_ \'_'N'
°°" '
o0_ ....._.,__.,.__,_ .,_,.__,_.___.,...,.-,_L'C._ "10 20 40 60.{'0 100 _L_O I_00_00 If/JO _.CO0 ',
-il ......v (a) flat fios_d a_.rafod_, (b) '/.3n',mdia cyba_ar
0/, II .,(c, !,CCmrndiacyhn_r20_ b I (d) i,,,o body,>. _Sti,_rn_h_:rt flat plate
l :",1%'1 ._,_.-_. 15 (Re):.;.;p (_ux {1_l'OfOl[ )& u,- o (f} sh,-rt ftal_ Hate. '
I vlt ( ;t_'piI 0.3 II (l]) ton_ fl;lt ptai._
.\\ (';_t_.;p)
0 /00 2'.g !:00 600 _t,iO E.C#J 'ti;O ODD
FIGUREIII-4 SEPARATIONSTREAMLINEANGLE
-31-
I_"." : ._'......... :..: :::.::.:::_ .... --,_:.tL ";,.: ........<,,........,,_,.,,,...+_........ :: ,:...:,:c....._,_:_ ' "_:.:." ...: :.,.::-'.'.J<,_",.--.:--.,_.'.:.,........:.--_..._..-..-..,-."_;.
00000002-TSC13
tl,_.,, I,I ll.' ;,. I, i_|tilirl., uDt.,l,i,'d t_! il, c I;,,rii',',i:i a|ilull ,,; _.
i,l_,,l'iii" .ll _llli !,{, (l_l.
_{ilu{l. e{p
FIuUI,E III-5 SEPARATION STREAMLINE ANGLE
-32-
--i-_li_'.;i":",.""" "" "" ....... ' "-""......-" -" :':!"::':*'""-:"--':'--:;'--'_' :- " :'--4
00000002-TSC14
OF pOOHQUALi'r_'
5Q@ ....... I-.......Io-rnqc_suredW_'Im_nne,rf_Jl
_# elrIo,, _ - ¢yllndor t
I ' _2_ _ " . . no,,, 1b°7 I I i i ,, ) b_,_(:cl,_Fod"
t. _ I_ J .=%, I . | ¢ylin¢¢, II :
_;_._ ^xlO=on =a I_¢m_=lonof <X;,),0ep 200 ............. '_ _j" "_'-_1_.;_ ,"e-",_--._.;_b_,moat:_,,,_' i'
_ZrI;o4l (O) .n,l thv cylIt,,Ior i r ,_...+,._. T,...Z_.:_...,.,._.tf_:,,ID,,-:, rich (&) .,)4 vL&hot,=(III) _,_.ra V_cenl u Plul | .... _. ....J .... '_. "' I _'
, o ........_ --_ "'--_ .... _o_'--',._-_oo'-'_ i
tS" &t
I)
1".;'
_e
_'00 4,00 Ht,__0_'
FIGUREIII-6 TRANSITIONBUBBLELENGTH
-33-
_;:_.= ." ::.............. -,_,,_ .... :::-.... :L:::: = _::-_"""--:: -::.........:-"""_____':'"ii'-" - _"""""" ": .... """""_:°"" ' ' ' i
00000002-TSD01
1ORIGINAL PAGE ISOF POOR QUALITY
L='
!
-34-
00000002-TSD02
ORIGINALPAGEIS
.....II:i-i.....i......Ii !....I.... -; i i '°'
* ! ,'_ I n _ I i'DLe"
.-- =^^_ ' /% ',_, , .
° ' ° ........'i0,4 ¢,6 0,0 I _ 4 _,; 1,3 I
rl. Vnrinlion o£ l_tlh_le k,nl_lh I_tll h_or, d.ll'_.lc|ycl' P,o)'II_,_IOIn|lml_cr It ! 4 b 0 7 0
,_,. ,_,8x tO*o
tOO0 .......... "*'1".... "T'-" "_""--"*'_1 ........ n IOt`
/I
0,2 600 _-.:.._"- -- -I IO_
_,, .oo_......t..... --:-_---,_---,' ---i ,°' "
I ....................0 _" ?00 ................ , , I I0
I k_L_] _ !. (,_,.o,.}
L 4 5 0 ? 6 P _ot_, a, deq
i_o _!_l _"
_' C,_,,'t,1;He_$|_,,umt'.',y-l:tycr Rcym,ld._mm_hcr at scpnr_tlm',, ]en,t',th _r
_ _ ,, _'3× ltP.
t_r,_,_:' ,.,_._ _ IrOOf O.S ...... _....--'_,,_,,_-_.."......'----__._0
.....'........'....... ! _.L/'b..i
,-_. I _, ¢ 5 o:-_ , I0 "° R
: Calcul_tcdb_ttnd;_ry.l,tycrP,_).no|clst'e,m_bcr=_t,_¢|,,II',HIL,n, '._.,o_._'_t11or
5ubhle nr.dp:-c_1_'_,rc:c_chv_ecl'fi:(onIr,,rX..'_CA_.ols _<,_,._,,i;:,,,<_ionnt ,t - IS°,
FIGURE lll-l_ TOTALB" ,I.F lENGTH
-35-
00000002-TSD03
11ORIGINALPAGEISOF POORo"_ IT:Y
blLP HF,IGIIT _iO_,nIN.El _ t, "0 13U IN...................... 0"._0............ - ......... " -
O.?b .........................if" O'Pfi............................
O'F.-q . / ._--_"_-- "I_ i.....-I- .- o,_c .,__f............... AI Vnri:,thm of
0'I_ .....l ...................... 0'15 --_I.......................... lllld_r/ I will! I_,
o,i_..........................._io i/.......
oo,,.........................°'°'_.................._o:,_,,_,,,_ , i,1 I
L........... _oa-'-----_ob.... Ioo " ' 030............."*_ '_ ......I........boo s__ ,oo I"s \@
!:
0.1,-...........
I
i .......- '.....; ,t.'_o! _-----__ I ,_'_D i . . _o#- i ,_" o.,......___--_ .......................',........
I : I I II !I ] I Ii , . i I ....: ;' ' I 'oj..........ZoO 300 ,tOO bOO
l_Osop
= !0,1 ,_------T'3.0.4.2, 7,6 o; ii i :ii i' ! I B ,,,°.,,.o,_o,o,,.oo._.._o,.o..' I I .(Eq. 31) an4 G1.ntor;_pre_;.;_trogradientII I I ! 'I " : J ,, , [or clo:_;.,d'separ,,th_n bub!,h,, , --'- == p,_rdl...t_r . .
O I 2. $ on th,' _¢vrt::.._an n[r_oil,I0"_R
C V_riatlonofpressurerccovcwcoci'lldehtwithR_noldsnumberetcoastantlncklenccs.Crabtrc,z's_,n_'lysis_) of cxp_!,'_nl,_,ld;tlaon McO_c_.ot_s
I |051 model.
i
0*4 r .... _ ...... r .......... -
" I i i. I I-- .,"_I I •: 0'$ .... _ -_---,---....I-....t?
• _ 0._ ....
I ! _1 ,
I 1 ,0 .... ' ' J
±_ O V_:ri,_lionofpre_:_re rcc,werF ¢ucffici,,:,t',_ilhincidenc¢at _ -,1.7 x I0_.
_' Cr,tbtrcc'san.ol)'rb,_:_ of M.:Crc_:e,'s expcrh:,_.mql ,I_t,t cn a T';crcyaerofoil.
FIGURE III-9 CRITICAL BURSTING PRESSURE COEFFICIEb!T
-36-
, ",, ._ _:';"_""-':_:"'"'_"'_" '..... "......... "_...................... _--" I_................ " _ fr i 'i -'_ii_.'iiiiiiII i i " i i I I I
O0000002-TSD04
_'l'i_Ai++,,+.;,.,,, t i
ORIGINAL PAGE ISOF POOR QUALITY
/
t-F D
,. I • +' ,, aO " _.... ' _ I: n h o [ F o I_ +.
(_ o +IIQ t' 61 0 P• 0 0 H¢r r_l Irlp i_
,;11, "1° ',, ,, ,lg' ,. ' o o in ¢ ,.1+" , r, _I n_' r, i o ++o n"
..... ,,, ?, <_ ,.,., _° _ ,,i, t- poi+
I t t.| .... -I n lit ,+, . _, ,,, ,.. .l .,,..,....i ,+ ,\ ,+ ,:I i- " _,i _',1
',ls,lllt_,,i, ++If,,,_,l Ill.hi • .il +i,lll1111++)Ijili.i I",I:l'li+lllIH,_i si"l'l b0l,l,h
L' i'. ++' +,,+;i ,s,,,,,+.iql,+l,,.il: h _+ ll..'ll I l,.,,h,,,,+ +,I, '. l,,,,hl,++,,tl'+i,,,,i,.sp,.,+_+i, l.,,,,,li,,'i_+di,IHh.hh1_+,
1' lhi+'i +_++,,l+i si,slrpillll,,+tll,% II "t_
...... ":I< '<"" .... '+itO l'i Pi 111% ¢1"1
I_" ct, X-12 l, X'1? e¢ o
• ! °B + B _ o, ., . lz 0 + .... iti,,+ I:'I I.,
" " -a -"+i A "a o co - + A ,I ',, <'(+ 0 0"_ 0 0 0 +.) 0 0
tl 0 ( 0
)¢10 0 0 0 P+) iO00 0 0 0 U"O 0 0 0 t
: '°'!::;+ L i , > ++, +<l I, : I ..... V- __t +..+. -.-t 1+_._i .... ,'_.L. -- l lX__L+__a.....a ,+.+
I'li .lllil ISp%+,'tlllli), lil,lhll"_ ,it tl*ltlllUt +l|l.llllA hv llllXlllilll%ll,ll I tilllll, ( h,,I,+lili+e tiltkll) lu,,h!. ', ,11I .ll i, iIl,i +lp,li ++lispII IIllllil|_l111 t +lillilt
ll'ili I'mll hllhhh' ll.iii l.. Bl,ilt i.'
I:, | I h +.%, • |' ]4 It +,+.+.,'1_+,l',i,I (l)_'/I,al)
I t"lt., iitltl II. t I. til+,, ¢In 0 ........ -i_ '
I II i,i X*l"lj`,iit II,_o I. I', ll" i_ I it I+_ _ O B
I " --"<1 " ° " +_.., _+ o ti l + --......
+_iil i.: " I J ,+. o t) i+ o° o o o° ."
"Ill t ,, , l, 0 I<++ r+ i I , )v 0 0 0i+
,, ,, o Z ............ "<1 + "
1 (+ o l ,.. C, n ,: o o u 0
,+ .. , ,+, o ,+ o° i_' o _ ""
i <, <, o <_ ,.+ o ,.+ <' / +o,,+.,.,...,,
o o t U*?t Ill +.v'-
I '_, '. _ ° o "_. o° _ _, _ •.... " ' _ 2 X._i_ir, t)
..... <, ,,,.<.<'.,.<¢- <.o1' tl () " -
I ' :_.... t .......i ---P _.... i. _i ++__ .l ..... + .......
..... , ++, , , o ,t -[", ,v '?V, t lu_..lv,-,e It'll'. Ilil i 'llllll` + .ll i,llltlllS illsIIIk_lll IId+itlidil •+
%[_IIIAI++k+vii I It+ I ,I It %,1! i Ill it ,+++;'+11111It'l+ll'l_l''
FIGIIP,F tit-ll BOUNDARYLAYERVELOCITYPIt'FILE
..38-
I
OOOOOO02-TBD06
ORIGflNALPAGEI_IOF po,- . .O_JALITY ,,
t
'
, 1.b!o.lo .... .
D'V_nkate;warlu [11l ,
: ftin [12]0.05 -.-. O Bur_n_ll& I.o ,-" ......
X .ult['r]l .. ,,,: i
:1 l _LL0 ........... " l_____..____1- . ._,.l_._ml j i • ..... L- | ,W.I_..P o_ _,
400 " 500 600 700 800 900 1000:. ,'
"" R0slFIGURE III-12 - Bubble Len£1tk ' "" , '
s'
• v
D Ven'katE_swarlu[11] '" ' iO Bursnall & Loftin [12] ,.
6 -- A Gault [7] I . . ,_,"4'. '
\u . htl 4.exYo6i-4,1"14 - _.=1_-_: - : _-....6
lid 2 -- ' '-
i-) . , _ "
_) IxlO3 1.5xlO3 2 xlO_ 2.5xi0 3 ""
,oiC:-I,_,
: FIGURE Ill-13 - Tr_nsil:ionCriterion Ba_'edon Bubble lle_ghtand
IL Reynolds I_lur,lbf,r. .. " :
'" - 39". i',
_._ _" "''" ?.; " __ .:........l,,,.'.'v" ,' "; ', ........
00000002-TSD07
ORIGINALPAGEISOF POORQUALITY
-41-
00000002-TSD09
ORIaINAt.eAG_I_ !' OFpoO_qUA61._
1
-47-o
,_-__.
• :• _ ....... - . ,......... ,-,,,- ....", ",-,' , ,,,,...._'"ii, '_"i ......... [I" "--n- I ....... I
00000002-TSD10
FLONSEPARATIONBIBLIOGRAPHY
III-I Prandt],L, - Verh.3d Int,Math_.angr- lleldaIbergTran_latedas NACAT_chnlcalM_mora_-_B_m452
te
!II-P. Prandtl,L -_hre, 4th Edition.Frledr,VIewe_,_-_raunBcllw_l g I.q44
III-3 Milllkan,C. B. & K1¢_In,A, L, - "TheEffectof Turbulence"AircraftEngi_erlng,Vol,B, No. 8, August1933,p, I(_g-174
III-4 Jono:_,B, MOlvllle- "Stalllng"- Journalof theRoyalAoronautlcalSociety,Vol.3B,No, 285,Sept,1934,p, 753-770
III-5 yon Karman,Th, & Mi111kan,C. B, - "OnTheTheoryof LaminarBoundaryLayersInvolvingSeparation",NASARep,No. 504, 1934
III-6 yon Doenhoff,AlbertE. - "A PreliminaryInvestigationof BoundaryLayerTransitionAlonga FlatPlatewithAdver;ePresSureGradient",NACATNB3g,1938
III-7 Schmitz,F. W. - Aerod_',,amlcsof The ModelAJrpiane.Part l-AirfoilMeasuremen-t's'_,'LudWigPrandt1Pr1zefor Ig41,translationby RedstoneScientificInformationCenter
III-B Pfenninger,We - "Investigationson Reductionsof Frictionon Wings,In ParticularBy Meansof BoundaryLayerSuction"ETH Zurich- Translatedas NACATM NO. 1181 ._
IIII-9 Maekawa,T.& Atsumi,S. - "TransitionCausedby the Laminar 1
FlowSeparation"- NACATM 1352 ,'I
Ill-t0 Bursnall,W. J. & Loften,L. K. - "ExperimentalInvestigationof LocalizedRegionsof LaminarBoundaryLayerSeparation", ..NACATN 2338,AprilIgsl
III-ll McCullough,Go B. & Gault,D. E. - "Examplesof ThreeRepresentativeTypesof Airfoil-SectionStallat Low Speed",NACATN 2502,SeptemberIgBl
m 111-12 McCullough,GeorgeB. - "TheEffectsof ReynoldsNumberon theStallingCharacteristicsandPressureDistributionsof FourM,_deratelyThinAirfoilSect.lens".NACATN 3524,November1955
_,,. lll-l:; Gault,DonaldE. - "AnExperimentalInvestigationof Regionsr: of SeparatedLaminarFlow",NACATN 3505,1955
'i
, Ill-14 Norbury,J. F. & Crabtree,L. F. - "A SimplifiedModelel_the iIncompressibleFlowPastTwo-DimenslonalAerofoils with a Long I
• BubbleTypeof FlowSeparation",RAETech.Note.No. Aero2352,June1955
-43-
""'"_ " "" " " _,;_-_._"_';_!,_;,,," ":"v,'_''_,," • ",,,,-:_":_;_--_......"_::: ",',.,:,"" -....................• " ""' "....... " t
00000002-TSD11
III-15 Ct_apman,DeanR., Kuehn,DonaldM, & Larson, HovlardK."Investigation of Separated Flows In SupersonicandSubsonicStreamsWithEmphasison the Effectof Transition",NACAReport1366,1958
Ill-16 Moor_,T. W, F, - "SQmaExper.im_ntson the Reattachmentof aLaminarBoundaryLayerSeparatingFroma RearwardFacingStepon a FlatPlateAerofoil"
,, II
III-17 Burrows,F, M, & Newman,B_ G. The Applleatlonof Suctionto a Two DimensionalLaminarSeparationBubble",Miss.StateUniversityAerophysicsDept,Report#27,Oct.1959
III-IB -Tan,,Itero- "LowSpeedFlowsInvolvingBubbleSeparations",Progressin AeronautlcalScience,Vol.5_ p. 70.103,'Pefgamoh"Fress,T9_6-4..... I I I
Ill-19 Morkovin,M, V. -."FlowArOt=ndCircularCylinder- A Kaleidoscope' I iSof ChallengingFluidP1enomenaSymposiumOn FullySeparatedFlows.
ASMEConference,Philadelphia,PA,May 18-20,1964
III-20 Roshko,A. - "A Review of Conceptsin SeparatedFlow",CanadianCongressof AppliedMechanics,Quebec,Hay 1967
III-21 Gaster,M. - "OnThe Stabilityof ParallelFlowsand theBehaviorof LaminarSeparationBubbles",PhD Thesis,Universityof London,1963. Alsosee BritishARCR&M 3595,1969
III-22 A.G.A.R.D.- "FluidDynamicsof AircraftStalling"ConferenceProceedingsLisbon,Portugal,Apeil1972
III-23 Laine,S. K. - "A TheoreticalStudyof the Effectof a Stepin a FlatPlateUponthe LaminarBoundaryLayer.NumericalSolutionsof the NavierStokesEquations",Dr.of TechnologyThesis,HelsinkiUniversity,Finland,1972
III-24 Dobbinga,E.,van IngenjJ. L., Kooi,J. W. "SomeResearchOnTwo DimensionalSeparatiOnBubbles",..Foundin ReferenceIII-22,1972
III-25 van Ingen,J. L. - "On theCalculationof LaminarSeparationBubblesin Two DimensionalIncompressibleFlow",AGARDSymposiumatGottingen,May 1975,AGARDCP 168
Ill-26 van Ingen,Jo L. - "Transition,PressureGradient,SuctionSeparation,and StabilityTheory",AGARDConferenceProceedingsNo. 224,Lamlnar-TurbulentTransition,1977
III-27 Young,A.D.- "SomeSpecialBoundaryLayerProblems"20thLudw|gPrandtlLecture,Copenhagen,May 1977Z. Flugwiss_WeltraumforschI 1977Heft6
-44-
..... ' '" " ...................... " uuuuuuu TSD12
III-28 Muel]er, T. J. - "Visualization of the Separation and _;ubsequentTransition Near the Leading Edgeof Atrfol.ls", ATARConferenceLangleyResearchCenter,March197B
III-29 Batill,S, M. & Huellar,T, J, - "Vlsualixationaf the Laminar-TurbulentTransitionin the FlowOveran Ail"foilUsingthe Smake_WireTechnique'",AIAAPAperB0.0421,March]980
III-30 Venkatesworlu,K, & jiarsden,D, J, - "Predictionof BoundaryLayerDovelopm_ntIn tho Presonceof a Laminar._eparatlonBubble",Un'Iver._ityof Alborta,Edmunton,Canada,1980
III-31 Thompson,J,F,,Turner,L,0Boarde_,J, H,, Kwon,J, li,,andLong,W. S, - "NumoricanSolutionof tho Navlor-S1.oko_EquatlonsforArbltraryTwo-DlmensionalMultl-ElomentAir.f(dIs,"Lang]eyResearchCanter'ATARConferonco,March7-9,lg7B
III-32 Brown,F,NoM.- SeeTheWindBI_Universityof No1_FeDam, F(}r--t"IC_ne,Indiana,copyrlght1971,F,N,M.Brown
III-33 Russell,J, M. - "Lengtha,_dBur.stlngof SeparationBubbles",NASAConferenceon Sc'lenceandTechno]ogyof LowSpeedandMotorless Fltght, March 29-30, 1979
III-34 Herring,R. N. & Ely,W. L, - "ImprovedPredictionof Laminar
LeadingEdgeSeparation",NASAAdvancedTechnologyAirfollResearch. Vol. I CP-2045, Hamptor,,,VA, March 7-9, 1978 ...
III-35 Gross,L. W. - "ThePredictionof Two DlmenslonalAirfoilStallProgresslon",NASAAdvancedTechnolo_AirfollResearchVo].I CP-2045,Hampton,VA,March7-9,1978
-45-
L i
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00000002-TSD13
I
IV, LOW REYNQLDSNUMBERAIRFOILCHARACTERISTICS
A. LABORAT{]RYTEST DATA
HistoricalRev_nv1
In the first two d_cad_ of the century,the early state of wind tunnel
d(_vel(_pmellto_aslonud te._tln.qat ,_fficientlylow Reynolds
number_to h_ _f l.ntern_tto thi._._:udy,R_f_rencesIV-l, 2, and 3 orb
frnm thlB nra, The turhulencnInv(_IBof the_e facilitieswere lower
th_n tha_ for thi_ p_rlnd in the Unlted State_,but even so,required
,I_ome_orrectlonto an (_ffectlveRoynold._numberhigher than the actual
t()_tRoynold,_number, Alt;hou,qhno_ a ri_Iorouscorrection,the data
_hown In Fi(IureIV-I Indlcate_good correlationof higher turbulence
testdata shift()donly in RN with accuratelow turbulencetest data.
Referen_:eIV_I is a very early s(_tof systematicdata showingthe effects
of thicknessand undercamberon sharp nosed airfoilsat a Reynolds
numberof 40,000, Tlleseresult_might have been lost in the mist of
timewere it not fo_ the sharp eyes of Krou_ein ReferenceIV-C, D and H.
Likewisethe systematicairfoildevelopmentsof WWI of referenceIV-2
might l_avebeen lost _o Americanr,_odelalrplanebuilder:,had not !:
Dr..AlexanderLippischrememberedthem. He spent many hours pouring '
over.theold data and selectlngthe most suitablefor model airplanes.
His gift to Americanmodel builders,referenceIV-7, lackedonly the
correctiontO effectiveReynoldsnumber. This led to somewhatopgimistic
performancepredictlons.
The first real understandingof the low Reynoldsnumber problemon wing
sectionscame with the work of Schmitz,referenceIV-4, Continuouswind
tunnelrefinementto a turbulencelevel near that of free flight
revealedthe difficultyof obtaininggood airfoilperformanceat
low Reynoldsnumber (17,000-_80,000)in the absenceof hl.ghambient
turbulence, He discoveredhysteresisloops in the lift and drag values
of airfoils_n the criticalflow regimeand the effectivenessof artificial
turbulenceproducedby a wire in decreasingthe criticalReynoldsnumber,
He providedthe first attemptedrecomn_.ndationof optimumvaluesof .....
airfoilthicknessand camber,and their positionsas well as leading
edge radius,all as a function,of Rc, ReferenceIV-4 is the one funda-
mentalbook which shouldappear in a_y low Reynoldsnumber library,
-46-
O0000002-TSD 4
r_
1,6 ....... I ................,p ,....-... f" I
//i ............... tl ............
1,0 ..... / ...............- "'-'- " ......................................................e ['i
o,o................ .-- 3cl- R_ 12oooo tl,o,_........_,................... 1....... - ............. _'.............
•_" ,_-, 11--o/, ....... ',", i..... / I \
o,2..................F- i..... ) ......................... - .......
O(x
[-oo2.................._......I...........,_.....i..............................................0 0°02 0,0_, 0,0(; 0,08 - 8 - 4 0 4 e 12 ..0,12 -0,0:I - 0,0/_ 0 ,I
-_ L'_- CV/_ _. "-"U_.'-""(_m .--C._*""'CrN25
FIGUREIV-I
-47- !
O0000002-TSE01
Pfenningerin Z.richstudiedairfoilswith exten_ive,lamlnarflow, IV-5
with and withoutdistributedsuctionat Zurichin the early 40's,
l'hes_experlment,_in a low turbulencewllldtunm_1showedremarkably
low drag value._for 6'X,and q% thick laminarairfoilsat Reynolds
numbersbetweenIOO,OllOand 760,000. He also showed the effectiveness
of leadingedge air Jets, surfacewavltless,and rearwardfacingsteps
in the upper surfacein reducingthe drag at certainReynoldsnumbers,
The sole contributionof NACA to airfoilinformationat RN<700,O00
(once the importanceof ambientturbulencewas recognized)is tt_
data of referenceIV-6on a thick laminarairfoilshowingthe decrease
in performanceas the Reynoldsnumberis decreasedto a value of 230,000.
Suzuki of Japan attemptedfree air testingby use of a whirlingarm.
He experienceddifficultiesin reducingthe data to absolutenumbers
but felt the comparativedata was valuab'le.IV-8.
FollowingWWII, a group o_ model aircraftenthusiastsin Englanddid
extensivelow RN aerodynamicwork in three differentlow turbulence
wind tunnels. ReferenceIV-9 and IV-lg.
A very large systematicallyderivedseriesof airfoilswas developed
at G.E. in 1954and-testedat the wind tunnelat West VirginiaUniversity.
The data was shiftedto an effectiveReynoldsnuplbergreaterthan test RN and
is bslievedby this writer to be valid. This data is mo_t usefulin
studyingsystematicvariationsin thickness,camber,and form over a
RN ran_u of 70,000to 565,000. IV-lO.
Pfenningerreturnedwith a remarkabletest of a 4.8% thick,4.2% camber
laminarairfoil in 1956, referenceIV-If. These experimentswere done
if_a flow tube of very low turbulenceat a singleangle of attackover
m a RN range of 20,000_g2,000.He was able to show the beneficialef.fect
:: of multiplespanwiserunningchrodwisespaced tape stripson the upper
!-_ surfaceand the necessityfor placingthe first strip furtllerforward
.. as the Reynoldsnumber decreases.
_ Charwat_referenceIV-12,continuedwork startedwith Pfenningeron the
bird-likeairfoilsectionof VladamirSeredenskyand obtainedah
il excellet_tset of test data for 30,000_RN<110,000.
;
O0000002-TSE02
An extremely thorough set of tests w_e conducted by Kraemer who had
worked with Schmttz at G6etttnflen and may be thought of as a continuationof the earlier Schmttz work. Data from four different atvfotls wtth and
withoutartificialturbulen_:t_,wires ts presentedin referenceIV-13.
Additionalsystematlcand dotalledmeasurementson GBettlngenalrfolls
of _, IP.,16 and 20_,thicknesswere performedby MusemannIn 1959.
ReferenceIV-14.I
The measurementsat MississippiState University,referenceIV-15,were
conductedin an unusualfacilitywith the wlng extendingspanwlsebeyond
the edges of a free Jet.
An excellentreviewof a few alrfoilssuitablefor model aircraftwere ..
reviewedby Thies in referenceIV-16. The review by Rebel on 29 MVA
airfoilswith Reynoldsnumbersadjustedto correcteffectivevalues
plus 18 later Goettlngensectionsfrom low turbulencetunnelexperiments
representsthe best set of easy-to-readalrfollpolars available.ReferetlceIV-17,
StartMiley chose the designof low Reynoldsnumberairfoilsas his
DoctorateThesis at MississippiState Universityin 1972. He made some
measurementswith a model airfoilmountedon a sailplanein the turbulence
free atmosphereto confirmhis design theory. See ReferenceIV-lB.
In 1971 Patricksumarlzed softieof the work of the BritishLow Speed
Resea.rchGroup in an Americanpublication,IV-I9,since the limited
reportsof LSARA had long been unavailable.
AlthoughWortmannof Stuttgarthad been primarilyinvolvedin sallplane
airfoildevelopmentat RN = 700,000to 3 X 106, he did investigatean
excellentairfoil,the FX 63-137 at RN between280,000and 700,000,IV-20.
This sectionwas used on the BritishPuffinman power aircraft.
_= A largenumberuF airfoilshave been testedin a small wind tunnel in
Milano,Italy,by Bosco and reportedin 1972. IV-21
• Data from a low turbulencetunnelin Czechoslovakiaon the low cambered
_ 795 was made availableto model buildersin 1974 as well as the NACA.
4412. IV-22,-23. ,I
!
-49-
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O0000002-TSE03
Also in 1974 ttendrtcks wa._abl_ to Lest a complete A/2 model sailplane
in the low turbulen_:e tunnel at DOTft University in the Netherlands, IV-24,
In tile sameyear Do LaurJor and ttarrts a_ the Battelle Institute put to
rest the furor over the Kltne-Foolnman stopped airfoil reputed to have
magical properties by mea.surtng it as inferior to everything in sight, 1V-25
Model builders received some very useful new results tn 1976 when Phtlltp_
on _abbatt¢ol in England tested both the popular American Gard Ltnstrum
Phillips airfoil and the Eppler 3_7 in the low turbulehce wind tunnel at
Cranfleld, IV-26. This work was continuedby P_trick. IV-2_.
Meanwhile,a group at the Universityof WesternOntarioin Canadawere
attemptingto developlow Reynoldsnumber airfoilsfrom theory, A few
were testedIn a low turbulencetunneland reportedIn referenceIV-27,
The finestmeasurementsat low Reyno_.dsnumbersare presentlybeing obtained
at Delft University. Tests of five airfoilswere reportedIn reference
IV-29 in 1977. These resultswere comparedto G6 795 resultsin a paper
by Girsberger. ReferenceIV-30.
In 1978 the writer presentedsome long lost data on the thin lamlnar
Pfenninger048 airfoilwith multlpleupper surfacetrippersto modellers
in referenceIV-:_2.In the sameyear, he sun_arizeda11 availablelow
Reynoldsnumber,low turbulenceairfoildata in connectionwith the Mars
aircraftproject. ReferenceIV-31.
Prof. Marsdenof the Universityof Albertahas developedtwo differentlow
_ drag airfoilswith slottedflaps for high performancesailplanesand light
power planes. Hls measurementsextenddown to Rc = 500,000,where these
relatively-thick,alrfoilsare still performingwell. IV-33.
m McMastersat Boeinghas recentlydevelopeda thick symmetricalstrut
_ fairingfor RN.between250,000and 1,000,000. Tests have been conductedand correlatedwith theory. Refe.renceIV-34.
In 1979, Patrickof Englandpresenteda fine paper to the BrlstolInternational
RPV Conferenceshowingdata from the Cranfleldtests and new free fllght
data obtalnedIn the U.S. on radio controlledsailplanemodels. ReferenceIV-2,'_.
In 1980, Derlllaof MIT sent data obtainedon the Llssanen7769 Llebecktype
alrfollused on the McCreadycross-_l_annelman poweredairplane. The tests
were _onductedin an open Jet wind tunnelat a RN of 277,200, IV-35.
-50-
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O0000002-TSE04
In February19BO, Dr, van Ingen sent the latestdata from Delft University
on a curwd platewindmillairfoilwith tubularspar, referenceIV-36,and
the _agerlyawaitedtest data ml the very promisingEpplerE-61, reference
IV-3_i.This thin, cambered,theoreticallyderived(referenceBook No. 9)
sectionwas recomendBd for testingby the writer in 197B as having the
most interestingpote,1_ialfor effI,:ientflightin the criticalReynolds
number ranoe. The pr,._liminaryresuII,are most interestingand a more
completerepurtwill be availablewhen Mr, deVriesreturnsfrom militaryduty.
McMastersin referenceIV-3Hpresentsa fascinatingcollectionof aero-
dynamicdaLa on flyiwlgdevicesrangingfrom insectsat RN _ I00 to aircraft
at RN _ 10,000,000. Hls Low Speed AirfoilBibliographyreferenceIV-3g
is usefulmainly for the Reynoldsnumber regimeof 700,000and above.
Gooden,referenceIV-40,extendedthe measurementson a popularthick
Wortmannsailplaneairfoildown to RN = 500,000in a very detailedstudy
in the excellentDelft Universitylow turbulencewind tunnel.
ReferencesIV-41,IV-42, IV-43and IV-45 presentmeasurementsat Reynolds
numbersgreaterthan 700,000b_t-_e valui_blein boundingthe region of
interestto this report.
A1thausin referenceIV-46 presentswind tunnelmeasurementson airfoils
with flaps,down to a Reynoldsnumber of 700,000. J
In 1980 a largecatalog,referenceIV-46,containingcoordinatesand
perfor_nancedata for 30 airfoilsin the model aircraftReynoldsnumber
range becameavailable. The measurementswere made by Dr. DieterAlthaus
in the small low turbulencewind tunnelat the Universityof StuttgartmB
_ in West Gei_ny. A n_del chord of 4.72 inchesallowsmeasurementdown to
a chord Reynoldsnumberof 40,000while a 7.85 inchmodel chord allowsmeasuren_ntup to 250,000. The turbulencelevel is 0.08% of free stream
velocity.
Elevenof the 30 clean airfoilswere also testedwith a single two dimensional
trip strip on the forwardupper surface. Three of the models were tested
with trailingedge flaps at severaldeflections. Thicknessratiosvaried
evenlyfrom 5.?% to 15_ with an additional33% symetricalsection.
Cambervaried from 0 to 6.7%. Locationof maximumthicknessvaried
from 19.6 to 33.9% and locationof ,1_ximumcamber from 30.9 to 56.5%
of chord. !
O0000002-TSE05
Six sectionswere deslgnQdby Dr. F. X. Wortmann,three by Dr. D. Althaus
and nine by Dr. R. Eppler,all of Stuttgart. AIso includedwere two oldOt
Gottingensections,six old NACA sections,two Clark Y ._ectlons,plus the
Sokolovand K-2 Russiansections. This catalogis unique in having So
many sectionsaccuratelymeasuredin the same facility. Many of the older
sectionsare of interestbecausethey have been used by model builders
in the past. The new Stuttgartsectionsare of interestsince they
have been base4-_._odernboundarylayer analyslsconcepts.
Muellerof Notr_ Dame has been doing basic researchon low Reynoldsnumber
laminarseparationbubblesin an excellentlow Reynoldsnumbersmoke tunnel.
In referenceIV-4B he describesleadingedge separationonan NACA 663-018airfoilat Reynoldsnumbersof 50,000and 130,000.
At the author'sinstigation,Dr. Muellerdirectedgraduatestudent
T. F. Burns,referenceIV-49,to measurethe performanceof the Eppler
61 and Pfenninger048 airfoils. Using a force balancefor drag, the
measuredperformanceof these sectionswas markedlylower than previous
wake rake drag determinationsperformedat Delft and at Stuttgart.
These discrepanciesin data from three differentbut excellentlow
r, turbulencetunnelsare now being activelystudiedby Mueller. Resolution
of this problemmay have far-reachingconsequenceson futureexperi_ntal
: airfoilperformancemeasurementmethods.
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O0000002-TSE06
CHRONOLOGY
PRINCIPALINVESTIGATORS,LABORATORIES,REYNOLDSNUMBERRANGESAND AIRFOILS
YEAR INVESTIGATOR LABORATORY R.N. _ AIRFO.ILS REF
Igl2 Bairstow& Natl. Physics 4,40,000 Flat bottom sharp IV-IJones Lab England nose varioust/c.
Mid t/c upper surf.with variousunder-camber.
Igl7 Hunk & G_ettinqen I06,000 MVA 29 airfoils IV-2H_ckel Germany 128,000eff. variousthickness
170,000 and camber
1920- Langer& GBettingen 400,000 Large familiesof IV-31932 Schrenk Germany 680,000eff? airfoilsof various
thicknessandcamber
1937- Schmitz GBettingen 17,000to Flat plate_curved IV-41939 Germany 380,000 plat% 12%t 4%f and
20%t 6%f airfoils
1940- Pfenninger ETH lO0,O00 Laminart/c = .06 IV-51943 Zurich, 760,000 f/c = .027
Switzerland. Laminart/c = .09f/c = .029
1944 Quinn & NASA Langley 230,000to NACA 653-418 IV-6Tucker USA 9XlO6 a = l.O
LTT, TDT, & NACA 00127'xl O'
1950 Lippisch Goettingen I06,000 Reviewof Munk and IV-7Germany 128,000 H_ckeldata
170,000 29 MVA airfoils
1948 Suzuki WhirlingArm 45,000 Clark Y,6409,6412, IV-81952 Japan 120,000 G_ 500, 227
M6jR series_curvedplate
_: 1954 Patrick& Battersea 25,000- ISACSON64009 IV-9Keating Polytechnic 630,000 M.A.R.P.6309e
England1954 Deslauriers Univ.of W.Va. 70,000- 27 systematic IV-lO
1955 USA 565,000 variationsin t/cand f/c + NACA65-41065-(12)10BR,I0C4/25C50
1956 Pfenninger Low Turbulence 20,000- Laminar IV-llFlow Tube USA 92,000 t/c = 0.048
f/c = 0.042
-53-
I.
• _ ........ _ '- . - ._ , , , |= i I II ...... i
O0000002-TSE07
YEAR INVESTIGATOR LABORATORY R.N. AIRFOILS........ REF
1967 Charwat Low Turbulence 30,000- Sereaensky-bird IV-12W.T. at USC,USA110,OQQ airfoil
t/c _ 0.10Sharp I.e.
1957 Kraemer GUettingen 21,000 GB 801 t/c - 0,1 IV-13Germany 170,000 flc = 0.07
GB B01 paper coveredGB 801 with lowerl,e. cut-outGB 803 t/c = 0,06f/c : 0.07G_ 804 t/c : 0.06f/c = 0.067
1959 Musemann GBettingen 17,000- Go 795 796 797 IV-14Germany 410,000 798
t/c : 0,08 0.120,16 0.20
1959 Murphree Miss. State 150,000 Eppler No. 49 IV-15Univ, USA t/c = 0.07
f/c = 0.07
1963 Thies Goettingen 42,000 M.V.A123, 301, IV-16Germany 168,000 Go 795 Go..801,
801 paper covered,803
1965 Rabel Goettingen 21,000 29 MVA airfoils IV-17Germany 380,000 18 Go airfoils
1972 Miley Miss. State 600,000 Miley MO 6-13-128 IV-18Univ, USA
1971 Patrick 3 wind tunnels 32,000 LDC 2;LSARA IV-19in England 55,000 Droopsnoot,G_417a
BenedekB-8258bvB B-8356b_NASA 6409
1972 Althaus Stuttgart 280,000- Wortmann FX63-137 IV-20,- Germany 700,000
• 1972 Bosco Milano,Italy 41,800- Bo 545-310Clark Y IV-2160,000 Eppler385,3.8.7,392,
> Fukuda I0 Go 496,500, 546, Hill SR2
7. NACA 0009, 0012, 4212,4412, 6412, 6409
41974 Horeni & Czechoslovakia20,000- G_ 795 IV-22
Lnenicka 250,000
-54-
O0000002-TSE08
YEAR INVESTIGATORLABORATORY R,N, AIRFOILS REF
1974 Ln_nt_ka Czechoslovakia 20,000- NACA4412 IV-23250,000
1974 Hendrtcks Delft univ. 39,600- Gerontmo IV-24The Netherlands 60,800 t/c = ,0761
f/c - ,0724
1974 DeLaurier & Battelle Insti. 23,000 Flat plate, stepped IV-25Harris Columbus,Ohto wedge, NACAO012t
USA Circ. Arc
1976 Phillips Cranfield 25,000- Gard,Linstrum, IV-26Institute 80,000 PhillipsBedford_ Eng. Eppler 387
1976 Eggleston Univ. of 66,000 (A) t/c = .06 IV-27WesternOntario, Recoveryfrom 17%Canada (B) t/c = .06
Recoveryfrom 71%
1976 Patrick Cranfield ? Eppler 387 IV-281977 Institute
Bedford, Eng.
1977 Volkers Delft Univ. 60,000- Doublewedge, IV-29The Netherlands 500,000 curved plate,
FX66-S-196VIEppler 385 and 387
1977 Girsberger Goettingen 20,000 Go795 and IV-30Germany 250,000 Eppler 387
1978 Carmichael Capistrano 20,000 Surveyof 27 Low IV-3IBeach, lO0,O00 RN AirfoilCalif.USA Characteristics
1978 Carmichael Capistrano 23,000 Pfenninger048 IV-32Beach, 90,000Calif.USA
1979 Marsden Univ.of 500,000- MarsdenSF 154 IV-33m Alberta 1,200,000 cf/c = 0.17
Canada tit = O.154
_ 1980 McMasters BoeingAC 250.000- Symmetrical IV-34= USA 1,000,000 t/c = 0.288at .31c
1979 Patrick DelftUniv. 60,000- Eppler387on all IV-jIB_=_ 200,000
Cranfield Insti 40,000-I00,000
R/C FreeFlight62,000-320,000
1980 Derilla HIT Open_et 277,200 Lissaman7769 IV-3SWlndTunr,el
-55-
D j
n
C-' ,' ,':, ,,-i ,L ,',- .; i_l i I I I :1 I Illl ill ii1' I/ III I Iii
O0000002-TSE09
Year Investigator Laborator_ RN Airfoils Reference
1972 Llebeck,R. McDonaldDouglaslO6 Liebeck IV-45laminarLiebeckturbulent
197B Althaus,D. Stuttgart, 500,000 60-126 IV._l_Germany to H-2
1,500,000 06513764,-012LIII-142K
1979 Bruining,A. Delft University60,000 Circ. ARC IV-37The Netherlands Plate
lO0,O00 I0% Camber200,000 6.67% C Tube
Spar
1980 deVries,J. Delft University50,000 EpplerE-61 IV-_WIThe Netherlands 80,000
1980 Althaus,D. Stuttgart, 40,000 to 30 Airfoils IV-47Germany 250,000
1980 Mueller,T.J. Universityof 70,000 NACA IV-48Bati]l,S.M. Notre Dame 66018
1981 Burns,T.F. Universityof 46,000 to Eppler 61 IV-49Notre Dame 210,000 Pfenninger048
-56-
\v ; "...... _.TI................ ...-,_a'..,..._.-._'_;r........,,_,i,' , "" ''; r':' " , , _m ,_ - " 1
O0000002-TS E10
DISCUSSION
In predictingfree flightperformancethroughuse of wind tunnel airfoil
data one must be aware of th_ pitfalls. Small changesin ambientturbu-
lence,tunnelnoise,model vibration,and model surfacecontamination
can have largeeffectson aerodynamicperformancein the criticalReynolds
numberrange.t
The data referencedin this repprthas been limitedto experimentsin
low turbulencefacilitiesor_ in some cases, to data where the Reynolds
numberhas been adjustedupwardby a factor based on the ratio (sphere
test criticalReynoldsnumber in free flightover spheretest critical
Reynoldsnumberin the particularwind tunnel).
When performancecriticalparameterssuch as maximumlift coefficient,
maximumlift/drag,maximum (lift)3/2/dragor minimumdrag of various
airfoilsare comparedone could easilybe led into a poor choiceof
airfoilfor a particularapplication. It is necessaryto examinethe
completelift vs. angle of attack curvesand llft vs. drag polar as well
as pitching_ments vs. angle of attackfor the entire Reynoldsnumber
regimeof the applicationin order to n_ke a wise choice. Some examples
of low Reynoldsnumber irregularitiesfollow.
-57-
°
O0000002-TS E11
Lift vs a and Lift Drag Polar Shap.3_
In the critical ;.,._..,lds number rftngo, lift vs. angle of attack
and 1Lft vs. drag curves undergo distortions relative to thQ
forms to _lltch we are accustomed at high Rcynolds number. One
can classify _he form_ in f/v_ cat_agorlos,sho_m In F$gu_e IV-2
and dlscnssod below.
CD vs. CL Fornl Description
A Almost constant drag over a largo lift raugo
AI Smooth drag Increases above and below designpoint
B Smooth drag decrease to a high CL desig_ point
C Noticeable drag increase in the mid CL r_ngo
O As in C'with a measurable hysteresis loop
E Rapidly increasing drag to_#ardvery limitcd
CL max
CI, vs. ci Form
A Linear, well behaved as at.high Reynolds number
B Nol1-1inearin the mid CL range
C Hysteresis loop in the mid CL range
D Hysteresis loop at or beyond " max_L
E Very limited CL max
Various degrces of the above distortions appear. It is possible
that some C form polars are nctually D type but that i_sufficient
data points were available to reveal the hysteresis loop. The same mf_ht
be suiclfor the B and C lift vs. ctcurves. In general, a given
airfoil's characteristics will regress from thc A or B types at
higher Reynolds number to the C, t).and E types _s the Reynolds
number is decreased. At a given Reynolds numbcr, excessive
thickness and/or camber is more likely to result in distorted
lift and drag curves than a more judicious choice. The B and C
type polars will often give the highest I/1_ and 1,3/2/D values.
-58-
tt*n
l
00000002-T$ E12
:LIFT DRAG POLAR FO_l4_
,.i.
cL eL,, q. q el." c_ _ c_
lIFT VS.¢i. l,'t,Rt..S
/ _
/ ( -/----,,&Jrm,jn,n -- :z: "_' -
A D c D E
FIGURE IV-2- 1IF" VS. DRAG A!,D lIFT VS._9'(Lkl'tS
-59-|
Lf: .........................
O0000002-TS E13
OF POORQUALIW
E type behaviQr (vory low perfoctnaneB) can occur with _ too thin, !
too little c_mhec aectlon _a well a_ wl'_ha too thick _ecglon and :
_hould ha avoided in the range 20,000< )_<i00)OOO, D _ype bohavlor i
ahould al_o ha avo_dud bocau_o of possible wild fllBht dynamics,
A modacaCo amoun_ of C behavior _eom_ to be a_oelatod wi_h _he
hiBh_mt L/D _nd L3/2/D airfOilu when _h_ R_ynaldu number i_ Juu_
ar:_lan_- and a_m porh_p_ ha _olera_d,
A very n_._p l_.ft, curve alnp_ J.n often found a_ nt_:_D.,e nng.lat_ of
a_tnck In the _r_lcal- I_ tangle, 'rhit) boo h,on ospl.oin_d by tim f
beautiful smoke pie,uriah take.n n_ No,re Dame by Burnn) ,hmnot'_) and
Muo_It_r,IV-49, Tho flow :If-)unabl,,to follow around a thin, throb(wad
airfoil nose ag nosatlvc a, The ooFnration t;au_e,.l a _ymmo_rtcal uhapo
of the outOr flow )inca. It ta at) _l' _he camber hau been _(_movod and
a _,_oop drop in lift occur_ over a small attgle of' attack ran8o.
b. J_P..J'J,ER E I___RRESULT,qIN THRE._LOWTU)_BtH.,_CE'rt)NN__.:L,_tqq
_1._t:__4____roduct i onq
The survey conducted by the author attd published in reference [V-31
pointed out the desirability of testing the Epple,_ 61 siace theory
predicted it to have low Reynolds re.abet performance superior to any
sections tested to date. ddYries, Hegen and Boermans, working unde_
the direction of Dr, van Ingen at Delft University, IV-36, in lhe
Netherlands, and Thomas F. Burns, working under the direction of Dr.
Mueller at Notre Dame University, IV-49,.have both conducted such tests.
The Eppler 61 wa_ also included in the large number of airfoils tes_e3
at._he University of Stuttgart) IV-47, by Althaus. ,,i
Ch_r.ac_a_isticsat R = 50,000c
Lift drag polat_ from the three facilitles..a.r.ecompared in.Figure
IV-3 at a chord.Reynolds number of 50,000. The Delft.data were
taken at 50,000, the Notre.Dame data at 46,421 and the 40,000 and
60,000 d_ta were averaged to produce the Stuttgart curve. Rather
pronounced C type behavior is noted. The Delft data give higher
llft and lower drag at optimum llft than the other two tunn_s,
and come very close to Dr. Epplerts theoretical predictions, IV-D-9.
The Stuttgart results are very similar but optimum CL is lower and
-60- i
_i_,,_ :.:.'._.'"." ' ..... ..: .:', L:_.: " '." - "_'""" .:,::,---:,':,:::::'-" ';. "'_:"..i :: ..... _f,._!" -_ .::':".":i::' -. " _ ,.i, :': -- "'i'",_-"_,"V_;"" '7 .... ,"_"_
00000002-TS E14
-61-
O0000002-TSF01
drag at optimum CL la higher than at Delft, The Notre Dame data
agree with the other two at CL = 0,9, but _h_ drag at optimum llft
does not fall back to a greatly reduced level as in the other two
tunn_ts° Differenea_ in (L/D) max and (I,3/2/9) max ar_ approalable°
Dol_t i,39 01.fl 72.8
Stuttgar_ 1.31 39°7 44.9
Notro Dame 1.20 14.8 16.2
|Characteristics at R = 80,000 |
The comparison at 80,000 Rc appears in Figure IV-4. The behavior
is still distinctly C type. The Delft and Stuttgart data are similar
but the Notre Dame data do not show any drag decrease above CL = 0.9.
The Delft and Stuttgart max performance numbers are now reasonably
close but the Notre Dame numbers indicate much lower performance.
Facility Optimum CL Maximum L/D Maximum L3/2/D
D_ift 1.4 63.6 75.3
Stuttgart 1.3 61.0 69.6
Notre Dame 1.2 23.1 25.3
-62-
.........• . '" .... 00000002-TSF02
ORIGINALPAGEIS
J-J
-63-
O0000002-TSF03
.Dy_._h)}:tp_tit}_)!2lftlle Throe Wind Tunnels
1 ' " T 'I ttml l)ol.ft ,_tutthart Notrp l}amo
'l'ypt, ? Non--rotur11 Non-roturll
t: 1"otit_ $4pc t I o11 tk_tJtgotlll I Rue t a1114111_11" Re,et an_Itl] ar
Ih,tght 4.1 ft 1.2,1 ft 2.0 l't
Width 5.9 ft 1.97 ft 2.0 ft:
l,eugth ? 2,02 ft: 6,O ft
t11"o88 St t:t. 1ollal 22.3 ft 2 2.38 ft 2 4,0 tt '2Al't','l
Power ? 1.0 ll.P. .1.5II,P.
/_ i} I° ill'l'urb. l,eve,I ,U...3a at 1'31 fps 0.08% 29.5<U,,'<88.6 fps
l,I ft: Measurement Strain (;age Balance Strain (;age Balance Strain Gage Balance
Drag bleasuremetlt Wake Rake Wake Rake Strain Gage Balance
blonlet_t b|ea stlremen t None None None
Other Oil Film -- Smoke Streams
The nle_lsttrellle|lt of drag by ,'..'_e balance method at Notre Dame could be
the explatiatton of one low indicated performance, llowever,.they did do
,1 lot of work oil repeatabil.tty and study of edge et:feet,'_. While complete
data was not "tvailable, the previous table reveals that all three facilities
-'Y are of reasonably low turbulence level. Since tile Notre Dame turbulence
i8 slightly higher than tile other two tunnels, we cannot challenge tile
better performance numbers at Delft and Stuttgart on tile basis of aII
31 turbulence induced increase in effective Reynolds number over Notre
Dame. As will be discussed in V, the ambient noise level eat 2 provide
I a large benefit in the critical Reynolds number range similar to a trip
-" wire. At present, [ do not have noise level measurements for Stuttgart
mid Notre Dame and only limited data for Delft.
,._" A_ mentioned lu the historical review, work is now in progress by Mueller
el Notre Dame which may shed light on the dtscrep_mt its between low
Reynt*lds IlUlnbor airfoil drag mt:asuremelltt_ urging strain gage or wake rake.
JI
-64-
"'_ '" " ,.. .. : ,- .,r.--._-., , .:_,..:_e ......... " '.... : 1), , ..... , .... ; -'" " ............. ";. "n"'('" I *,;
O0000002-TSF04
We can al_o compar_ results of tt_sts of two other Epplor airfoils
in t.ho Dt_lft', TV-29, lind _tuttgart, IV_47, tunnels,
Airfoil R_ynolAm No. (L/I))MtIx (L3/2ID)Max
llolft Stuttgart llolft _qtutt;gnrt
E°385 60,000 38 47.5 46.5 48l.O0,O00 63 q3 ?3 55
1.-187 60,0{}O :18 't6 Jfl 3hIO0,000 .55 54 55 58
The agrcemt, nt is qu:/to good for the E-387. 'rile differences tire greater
for the more heavily cambered 385. The differences are not predominately
in favor of either wind tunnel at either of tile two Reynolds numbers.
(c) Other rest Methods
It _s apparent that performance measurements of high performance airfoils
.j. in the critical Reynolds number range is tricky even using modern low
turbulence tunnels and instrumentation. One would llke to obtain the
data in tilenoiseless low turbulence regime of free flight. Free flight
gliding of complete models as discussed in IV-B provides the proper flow
regime but. is complicated by:
lW (l.) I,aunehing and flight dynamics
(2) Atmospheric motions (if tested outdoors)II1
m. (3) Uncertainties in calculation of induced= and parasite drag
_ One:would llke to see a test section developed (with strain gage balance%,
9 for lift and moment and strain gage plus wake rake for drag) and mounted
on some sort of noiseless vibrationless carriage. Perhaps a tensioned
I w.lre guided scheme with falling weight drive? The space requirements,
time at steady speed, and data recordlng/storage plan all constitute
,:ompllcatlons. One could well find new disturbance sources as serious
at_ tht_ uoi_e and turbuletwe problctu._ of the present tunnels. Still,
?lit' st'hetllt2 tier:8 I1O[ at_pt_Ol" llllpOS_tb,lt,.
-65-
O0000002-TSF05
(d) Alrft_ll Porfortaanco CnmpgUrt.apn___n
Tht_ vt_ry .l_lrgt _ amotmt: _lf .tt_w Roynt_ldn numbt_r tlSt'ft_t.l, d;lt_i aw_tlablo from
tht _, 1ant t_ovon dt_t, tld/_tl _illd frt_;n nttlo dlfft, rt*nt natlt_ntt will bo prt_aotlt:_ti
.t.ll t'tlllVOlltOIl|: fl_rra fol" tllo tlt_Hl.t_ll t_.llg.lnt,tw tn Vol.ttn|o II of thin ntudv,
-66-.
b
O0000002-TSF06
LABORATORYDATA BIBLIOGRAPHY
IV-I Balrstow,L, and Jones,B. M_Ivill- "Noteson the Propertiosof Airfoilsas DeducedFrom the Resultsof the VariousAeronauticalL_boratorie_".BritishR&M No. B3, March IgI2
IV-2 Munk, M, and H_ckel "Messargebnisseau_ den TocbnischenBorichtenT.B.I und _I der Flugzeugmoister_i".G_ttingenIgl7-1B
IV-3 Langer,R. and Schrenk,O."NeuereProfilunstersuchtlngen"and "Untersuchungweiteror Joukowsky-Profile"In - Ergebnisseder AerodynamischenVersucbsanstaltZuG_ttlngenIV LeiferungMunchenund Berlin_g32
IV-4 Schmitz,F. W. - Aerodynamics of the Model Airpla_Part I- AirfoilMeasurements_'Translationby Redstone_rsenal-No_."_2,-T96-7_ OriginalPublication- GBttingen1942
IV-5 Pfenninger,W. - "Investigationson Reductionof FrictiononWings, In Particularby Means of Boundary-LayerSuction"Translatedas NACA TM No. If81, 1946
IV-6 Quinn,J. H. and.Tucker,W. A. - "Scaleand TurbulenceEffectson the Lift and Drag Characteristicsof the NACA 653-418a = l.OAirfoilSection°" NACA ACR No. L4HII.WR L-138. Ig44
IV-7 Lippisch,A. M. - "Wing Sectionsfor Model Planes"Air TrailsPictorialMagazine- April and May 1950
IV-8 Suzuki,S. - "WhirlingArm AirfoilTesting"Work done in Japan.Reportedin Model AeronauticYear Book..byFrank Zaic 1955-56
IV-9 Keating,F. A. and PatrickT. - "AirfoilTest Work of the ModelAerodynamicsResearchProject." 1954 M.A.R.P.SymposiumReport.Also reportedin BritishModel AircraftMagazine,Feb. 1956 ..
" "AIV-IO Deslauriers,E. J. - Simple Blade ProfileSystematic"GeneralElectricTech. InformationSeries DF54A6T49B12-15-54and "BladePerformanceat Low ReynoldsNumbers"G.E. Tech.InformationSeries R54AGT6051-14-55
n
IV-ll Pfenninger,W. - "ExperimentalInvestigationof an AirfoilWithHigh Lift to Drag Ratiosat Low ReynoldsNumbers." NorthrupAircraft Inc,NAI 56-188ReportNo. BLC-84 Feb. 1956
IV-12 Charwat,A. F. - "Experimenton the Variationof AirfoilPropertiesWith ReynoldsNumber." Journalof the AeronauticalSciencesMay 1956
-67-
II I I illllllll .... " '_'- """ ' - - I [l" III11
O0000002-TSF07
IV-13 Kraemer,,K,,- "AirfoilProfilesIn a CriticalReynoldsNumberRegion"GoettingBnReportForschungauf dem GebietedesIngerieurwesensBd 27, 1961 Nr, 2 S 33/46
IWl4 Muesmann,G. - "Measuremen•tsand BoundaryLayer Observations_n aThickenedBlower Profileas a FunctionQf the ReynoldsNumber"Z Flugwiss7 (9),253.2641959
IV-15 Murphree,D, L. - "MeasurementsOn A HighlyCamberedModelAirfoilSectionAnd ExperimentalTechniques"AerophysicsDept.ResearchNote #8, Mi_s. State University,April 1959
IV-16 Thies,W. - "Fl_gelprofilemit geraderUnterseite"Swiss Aero Revue - January1963 and February1953
IV-17 Rabel,H. "ModellflugProfile"- Munchen 1965
IV-IS Miley,S. - "An Analysisof the Designof AirfollSectionsForLaw ReynoldsNumbers." MississippiState UniversityPh.D. 1972 -.UniversityMicrofilms,Ann Arbor,Mich.
IV-19 PatrickT. J. - "The Low Speed AerodynamicResearchAssociation1947-1954"FourthAnnualSymposiumof the National•Free FlightSociety.1971
IV-2O Althaus,D. - "StuttgarterProfilkatalogI."Institutfi_rAerodynamikund Gasdynamikder UniversitatStuttgard1972
IV-21 Bosco,A. - "AirfoilSectionsfor FlyingModels"
Ass,elazione Sportiva AeromodelIistica 20081AbbiategrassoMilan, Italy,December1972
IV-22 Horeni,B. and Lnenicka,J. - "AerodynamikaOpravdusModelarska"ModelarMogazine4/1974
IV-23 Lnenicka,J. - "Reportto Pierpontof NASA Langleyon the CriticalReynoldsNumberof the NASA 4412 Airfoil." CzechoslovakiaApril 1974
IV-24 Hendricks,F. - "AerodynamicMeasurementson the Wing of theGeronimoA-2." The NationalFree FlightSocietySeventhAnnualSymposium 1974
IV-25 DeLaurier,Do and Harris,J. M. - "An ExperimentalInvestigationofthe AerodynamicCharacteristicsof Stepped-WedgeAirfoilsat LowSpeed." AermlcanInstituteof Aeronauticsand Astronautics. 1974
_• IV-26 Phillips,W. H. - "Low Speed Wind Tunnel Tests of Two Airfoils, Suitablefor Models." NinthAnnual Symposiumof the National
Free FlightSociety. 1976
-68-
O0000002-TSFO8
iiIV-27 Eggleston, B,-"The Destgnof Atrfolls for HlghLift/Drag Ratios I!
at LowReynoldsNumbers."CASlSymposiumon RecreatlonalAlrcraftoToronto,Canada. September1976
IV-2B Patrick,J, T. - "Alrfol]sDown to CriticalReynoldsNumbersAnd thePerfor,mnceof RemotelyControlledGilders",BristonUKRemotelyP11otedVehiclesInternatlonalConference,3-5 Sept.1979
IV-29 Volkers,D. F. - "PrellmlnaryResultsof WlndtunnelMeasuremegtson SomeAirfoilSBcti_nsat ReynoldsNumbersBetwuen0.6 x I0°and 5.0 x 105." Delft University of Technology, Dept, ofAerospaceEngineering - MemoM-276. The Netherlands. June 1977
IV-30 Girsberger,R. - "Ergebnl_seyon Wlnd.kanalmessungenanModellflugprofilen."SwissAeroReview. 12, 1917
IV-31 Carmlchael,B. H. - "Surveyof Two DimensionalAirfoilDataBetweenReynoldsNumbersof 20jO00and 100,000."StudyforDevelopmentalSciences Incorporated. Ctty of Industry, Caltfo ..91744,April1978
IV-32 Carmlchael,B. H. - "A SignificantIncreasein Llftto DragRatioof Airfoilsat Low ReynoldsNumberThroughtheUse of MultipleTrippersandLow DragLaminarFlow." AnnualNatlonalFreeF11ght
SympOsiumReportFor 1978 i
Ha eden D - "Wi-dT - IIV-33 r , . , unnelTestsof a 15.4%Thick6LaminarAirfgil 1WithSlottedFlapat Reyno]dsnumbersof 0,5 x 10 to 1.2x 10°."
!Universityof Alberta,Edmonton,Canada. UnpublishedNotes.1979
IV-34 McMasters- "ThickStreamlinedStrutTestResults."Private 1Communication.February1980 '
IV-35 Derilla,M° - "Testsof theLissaman7769Airfoilat a RN of277,200in theM.I.T.OpenJet WindTunnel." P_ivateCommunl-cation. February1980
IV-36 deVries,J., Hagen,G. H. & Boermans,L.M.M.- "P_el!mina_Resultsof WindTunnelMeasurementsat Low ReynoldsNUmberson AirfoilSectionE-61." Dept.of AerospaceEngineering,DelftUniversityof Technology.PrivateCommunicationfromDr.J. L. van Ingen,February18, 1980
I IV-37 Bruinlng,A. - "AerodynamicCharacteristicsof a CurvedPlate'_ AirfoilSectionat ReynoldsNumbers60,OOQand I00,000and_ Anglesof AttackFrom-10 to +90 Degrees."DelftUniversity_. of Technology,ReportLR-281,May,1979.
_ IV-38 McMasters,J. H. - "AnAnalyticalSurveyof LowSpeedFlyingDevices - Natural and Man-Made". Proceedingof the 2nd Inter-NationalSymposiumon theTechnoloyyand Scienceof Low-Speedand MotorlessFlight. Mass.Inst.of Technology,September11-13, 1974
-69-
i " " ' ........ _ "'_ I I"II_IF"-''-_'- "" - |
O0000002-TSF09
!IV-39 McMasters, a. H. - "Low Speed Atrfotl Bibliography". Technical ""
Soartng, Vol. 3, No. 4. Fall 1974
IV-40 Gooden- "Experimental LowSpeed Aerodynamic Characteristics ofThe WortmannFX66-S-196 V! Airfoil". Technical Soaring, Vol. 5,No. 3, March 197g
IV-41 Btngham, 8. J. and Noonan, K. W. - "tow Speed AerodynamicCharacteristics of NASA6716 and NACA4416 Atrfotls wtth.35-Percent-Chord Single-Slotted Flaps", NASATMX2623
' IV-42 aacobs,E. N. - "PreliminaryReport on Lamlnar-F10wAlrfollsand New MethOdsAdaptedfor Airfolland Boundary-LayerInve=tigations. NACA ACRj April 25, 1939
IV-43 Loftln,L. K, and Smith, H. A. - "AerodynamicCharacteristicsof 15 NASA AirfollSe;tionsat Seven ReynoldsNumbersFrom0.7 x I0° to g.O x I0O_. NACA TN 1945, 1949
IV-44 Quinn,J. H. and Tucker,W. A. - "Scale and TurbulenceEffectson the Lift and Drag Characteristicsof the NASA 653-418= - 1.0AirfollSection". NACA ACR No. L4H11,1944
IV-45 Liebeck,R. -"Wind Tunnel Tests of Two AirfoilsDesignedforHigh Lift WithoutSeparationin IncompressibleFlow". DouglasAircraftCompanyReportMDC J5667/01,August 1972
IV..4:; Althaus,D. - "Measurementson AirfoilsWith Flaps at MediumReynoldsNumbers". TechnicalSoaring,Vol. V. No. 2. December1978
IV-47 Althaus,D. - ProfilpolarenFb_ Den ModelflugN V. Neckar -Verlao- Villingen- Schweinningen1980
IV-48 Mueller,T. J. and Batill,S. M. -"ExperimentalStudiesofthe LaminarSeparationBubbleon a Two DimensionalAirfoilatLow ReynoldsNumbers". AIAA Paper 80-1440,July 1980
IV-49 Burns,T. F. - "ExperimentalStudiesof Eppler61 and Pfenninger_. 048 Airfoilsat Low ReynoldsNumbers". GraduateThesis - Notre
Dame University- Indiaaa..January1981
-70-
' ." , . _ """ .:"'T_ ' _" _, _'_L_'_'_ "'''-'" " _" "" , ,.. _ "' - .... _J_l. ,_, I ......... I II I I I II II I ' II
O0000002-TSFIO
(B) DISCUSSIONOF FREEF_IGHTTESTING
It is moredtfftcul_ to obtatn rellable experimental atrfo11 data In the
crtttcal Reynoldsnumberregime than at higher Reynoldsnumber, An excel-
lent comparisonof three different experimental methodsts given by Phtlltpstn Reference 1V-59, The first ts the laboratory or wtnd tunnel approach
covered in the previous section. The remaining two tnvolve measurementsin free fl'ight, The first conststs of straight gltdes 'In a large roomOe OUtof doors, in which distance covered, altttude lost, and ttme are
recorded. The gllde ratio can be obtained from the forward speedand
the sinking speed, and, knowingthe wing loading, one can reduce the results
to a lift, drag polar for the completeaircraft. By subtracting the theore-
tical induceddrag and the estimated parasite drag due to fuselage, tatl
and trim, one can obtain the two dimensionalairfoil lift, drag polar, The
majority of the references in this section employ this method, The develop- !ment of a refined methodof thts type ts described tn Reference 1V-54..
This writer was privileged to witness this development,tn which the
student Hoffmenencouragedby Dr. GusRaspet andaided by GuySt, raP(all of Mississippi State College) slowly discovered the problemsand
cameup with Increasingly improvedsolutions. A sparta1 launching rat1 ']
withfallingweightacceleratorwas usedto improvethe steadystate,on
speed,on g11depathlaunch,so necessaryto prevent1ongitudlnaloscilla-
tions. The useof tworeferencehorizonlights,a lightIn thesldeof
_ the.modelaircraft,an opencameraplacedbeforea whirlinginterrupter ,i1
disk,coupledwith launchingin a darkenedlargeroom,constitutedthe
finalrefinement.The slopeof the interrupted11ghttracewith respectto
_ thereferencehorizongavetheglidepathangleandthe interruptionpattern
gavethe flightspeed. Thls typeof testingwas simultaneouslyand inde-
pendentlycarriedto the samedegreeof refinementby Maxlmi]lianHackllnger
m who obtaineda minimumslnkingspeedof 25.1cm/secand maximumglideratio
of 17 on a Nordic A/2 modelsailplane, References IV-35 and IV-71. Even
_: wheng11detestsarecarriedout In a largeroomone mustbe carefulthatthe resultsare not influencedby possiblemicrometeOro]oglceffects When
_. conductedoutdoors, thts problembecomesvery difficult Just as tn the per-
formancetesting of ma,,carrying sailplanes. As gltder performance Improves,(flatter glide slopes and lower sinking speeds) the percent error Intro-
ducedby vertical atr motion andalso horizontal wind tn ground referenced
-71-
i
" =........"'T_:_ _ _;_ _=x_':::_""'"_ _'_T'=_'_r_'-C "::.."!'... .......' _ ,, i, ,'_T;,,(_,°,:_';,_
O0000002-TSFll
measurementsbecomeslarger. The advantageof this stmple type of test
ts most pronouncedfor very low Reynoldsnumberstesting where glide islope_ are steep, roomstze requirements are mode_tmand internal tnstru-
mntatlon ts not possible, See for example H_ckltnger IV-71, tatlless i_microftlm mod_l RN- 11B0, Gibo and Pallett, deceasedbutterfly RN, 2700,
IV-70o Hackllnger IV-SBmIndoor Microfilm 3120_7310oRaspet-ZanontaSeedRN - 6000,IV-53,HarlandjMlcrofllmIndoormodelB,200_12tgO0,IV-64,
, McBrideIV.30,IndoorMicrofilmmodelRN - 12,800,BauerIV-_6,hand
launched.gliderRN - 15,000,and Newman,IV-BB,artificialdragonflywing,
12,000-,,60,000.
k somewhatless precise methodoften used by modelbuilders is to ttme severaldescentsfromthetop of a towlaunchlineof knownlengthin the early
morningwhenvertical air currents are not likely to be large. This ts
only useful for comparisonof different conftgurattonx and is fraughtwtth uncertainties. Nevertheless, tt was usedas the basts for the
statisticalanalysisof ReferenceIV-61in an attemptto definethe
mostsultableairfollselectionparametervaluesforA/2 modelsailplanes.
A morerefinedoutdoorglldetesthas recentlybeendevelopedfor radio
controlledmodelsallplanesby Rawdon,IV-69. Eachmodelis flownseveral
timesat a givenlongitudinaltr_msettingovera course. Groundbased
recordingof starttimeand altitudeand f_nlshtimeand altitudeare
madeforconsecutivepasses,180° differentin heading.The lattercancels
out thehorizontalwindbut scatteris stillintroducedby smallvertlcalair currents.
PhillipsinIV-59describesa methodwhichIs insensitiveto airmassmotion.
It obtainsthemodeldragto liftratioas the tangentof thesum of a free
floatingvaneangleanda pendulumanglewherethe formeris measuredfrom
thelongitudinalbodyaxisand the latterfromthe normalto thisaxis.
It Is necessaryto placethe vaneoutsidetheupwashfieldto thewlng
or to correct for it, and it is necessary to dampthe pemdulumand onlyread whenit ts steady. Although thts methodhas not beenwidely used
as yet foreithermodelor man carryln9sailplanes,it wouldseem%o
holdgreatpromisefor freeflightmeasurements.
i .
O0000002-TSF12
CHRONOLOGY
FREEF,LIGHTTESTING_
YEAR INV£STIGATORTYPEOF MODEL..... WINGSECTION RN .... REP
1934 McBrida IndoQrMicrofilm CurvedPlate IV.50
19BO HQlbrQQk Handlaunched Sore_n_kyAirfoil_001000 IV_61.glldnr DlffusorTip
Flying Wing
1951 Jex Tow llnoglld_r SL 6205NACA6409 60,000 [V=5_I.SARAS II andS II Rever_ed
1953 Rasper ZanonlaSeed Membrane- Single IV.B3surface AR _ 2,65
1954 Hoffmann Tow lineglider NACA4612 40,000 IV.B45" chord 60,00045" span
19S5 Hacklinger NordicA-2 Hacklinger 30,000 IV.B5ModelSailplane
1956 Hindes Tow llneglider NACA6409 40,000 IV.B6
4" chord !48" span
19577 Anon ModelSailplane Flatbottomt/c = IV-B7 i0,093 AR = 8.4 !
1964 Hacklinger IndoorMicrofilm CurvedPlate IV.,BB !
1970 Phillips R/C Model 200,000 IV-59Sailplane Not GivenNordicModel 30,000 !
Sailplane "11971 Ovelmen& Wakefield NACA6407,5 30,000 IV-60
Meuser Aspect Ratio - 19.2 t
1970 Allnut & Nordic A/2 Model 21 Successful 40,000 IV-61 ,Kaczauowskt Sailplanes Airfoils
1974 Hartman No_dicA/2 Model Eppler 58 & 59 40.,000 IV-62Sailplane plus three other I
camberroods. t1973 Ntppert 3 Nordic A/2 model Not Specified 40_000 IV-63
Sailplanes
• -73-
........ 00000002-TSF13
YEAR INVESTIGATOR_PE OFMODEL WINQ5ECTIO_ RN _F ....
1975 HAMan _ndoorMIcrafllm CurvedPlate fi,200 IV-64" 12,_0
1975 flad_s NordicA/2 Model B-B4BB-fat Root 42,B00 IVy66Sailplnn_ B-6466-fAt TIP
1970 Bauer PapOrhand-launchedThinPlato5nctlon30,000 IV-66
Balsahand-launched_ ElementAlrfol1_16,000 iG1idOr_3 NordicAI_ On_wlth_ _Iom_nt4O,OOQSallplano_ airfoil
1976 Bauer NordicA/2 AB-@O0B CH407 80vO00 IV-67SatlPlano_FAI PowerModel _ Element Atrfotls 70,000
1976 Newman, Indoor'Glider McBrideB-7Curved35,000 IV-BBSavage& 40" span plateSchouella 5" chord Dragonfly 60,000
1977 Rawdon RadioControlled NACA6412 2R-12 62,000 IV-69Sailplane Models Rawdon12.5%t 320,000
3%f
1979 Gtbe& Deseased Flat Plate 2700 IV.70Pallet Butterfly 4900
1955 Haekllngor NordicAI2 Model HA-12 39,000 IV.71Sailplane
1961 H_,cklinger NorelcA/2 Model. HA-12 39,000 IV-72SailplaneMicrofilmTatlless CurvedPlate 1150
-74-
Iii_ _=='_ , , .... _ ,._* • • . ." ' " ...... }_?.L/..._.j.?. IF' T.;' E L I.. " " '_.... _. ' ,4
_-. ..4". _ .'_.......... " ' ;/ "__'_' . . . ,_.'........ _'",,, p" ',........... _,",""-, T_" =
O0000002-TSF14
; FREEFLIGHTBIBLIOGRAPHY
IV-B0 McBride,J. W. - "SomeTechnlcalNoteson the PresentIndoorAlrfol1"- In JuniorAeronauticsYearBook- By FrankZalc
L Ed. 1934
_ IV-B1 Holbrook, C. T. - "SomeStudies on Flytn9 Wtngs._ IAS Student;_ BranchMeetln9at Tuscaloosa,Alabama.Aprll21 22, 1950
C IV-52 Jex,H. - "NarwhalGlideTestResultsat ReynoldsNumber=
, ' 60,000." Tests Conductedat Mass. Inst. of Technology- 1950-1q51IV-53 Rasper,A. - "GlidePolarof a ZanonlaMacrocarpaSeed." Indoorglide tests conductedat MississippiStateCollege,1953
IV-54 Hoffman,Gilbert- "AerodynamicMeasurementsat ReynoldsNumbersBelow100,000Obtainedby a FreeF11ghtG11deTechnique."Presentedat 5thAnnualSoutheasternIASStudentBranchMeetlng.April1954
IV-55 Hacklinger,M. - "Effectof Turbulatorson theG11dePe:-fornmnceof an A-2 ModelSailplane."Presentedat the 1955Low SpeedAeronauticalResearchAssociationMeeting. R.Ae.S.Library-London,England.November12, 1955
IV-56 Hindes,S. - "GlideTestsResultson a ModelSailplane."Presentedat the 1956LowSpeedAeronautiCalResearchAssociationMeeting.London,England.M.A.R.P.Report
IV-57 Anon- "GlideTestsof the BasiliskModelSai]plane."BaslerSchulen- SwissAeroReview
IV-SB Hacklinger,M. - "TheoretlcalandExperimentalInvestlgatlonof IndoorF1ylngMOdels."Journalof the RoyalAeronautlcalSociety.November1964
IV-59 Phillips,W. H. - "Experimentson Methodsof Measuringthe LiftDragRatioof Airfoils."NationalFreeFlightSymposiumReport.1970
IV-60 Ovelmen,S. and Meuser,R. - "TheFlightTestingof 13 WakefieldPropellers."- IncludesglldeteStof model. FourthAnnualSymposiumof theNatlonalFreeFlightSociety.1971
IV-61 A11nut,P. J. and Kaczauowski- "A RelationshlpBetweenBasicAirfollParameters/AspectRatioand Rateof Sinkof NordicA/2Gliders."NatlonalFreeF11ghtSociety,ThirdAnnualSymposiumReport. 1970
IV-62 Hartman,P. A. - "IntuitiveAirfoilTheoryand ConstructionofSolldWings." NatlonalFreeF11ghtSociety.SeventhAnnualSymposiumRepcrt. 1974
IV-63 Ntppert, V. - "Indoor Nordic Glider Tests." National Free FlightSociety Digest. November1973.
-75.
00000002-TSG01
IV-64 Harlan,Ro B. - "DragElementsof IndoorModelS" NationalFreeFllgh_SocietySymposiumReportfor 197S
IV-65 Hadas,A. - "AerodynamicCharacteristicsof a HighLiftTwoElementWing- An ExperimentalStudy.' NationalFreeFlightSocietySymposiumFor Ig7s
IV-66 Bauer,A. B. - "TheLaminarAirfoilProblem."NationalFreeFlightSocietySymposiumReportfor 1975
IV-67 Bauer,A. B. - "FunandGangswith FAI Flappers,"NinthAnnualNational2teeFlightSocietySymposiumReportfor 1976
IV-68 2¢ev_nan,B. _,, Savage,S. B., andSchouella,D. - "ModelTestson a WingSectionof an AeschnaDragonfly."McGIIIUniversity,Montreal,Canada. Ig76
Iv-6g Rawdon,B. - "PreliminaryReporton L/D Trials."PrivateCommunication(to be pub)Ishedin the 1981NationalFreeFlightSocietySymposiumReport).Ig7g
IV-70 Glbo,D. I. and Pallett,M. J. - "SoaringFlightof MonarchButterflies,DanausPlexlppus(lepldoptera:Danaldae),DuringthelateSumer Migrationin SouthernOntario."CanadianJournalof Zoology,Vol.57, No. 7. 197g
IV-71 Hackllnger,M. - "Flergmessungan elnemSegelflugmodell"AerodynamlscheVersuchsanstaltG_ttlngenDated30.4.1957.TestsPerformedin 1954. Alsopresentedat LSARAMeetingR.Ae.S.Llhrary,London,EnglandNov.12, 1955
IV-72 Hackllnger,M. "Gel_steund ungel_steFragender Modellflugtechnlk"Winnerof Otto-llllenthaland ludwigPrandtlPrize. DesBuchderluft@ahrtundRaumfahrt,BondVl,DeutscheVerlags-Anstalt jStuttgardIg61
IV-73 Czepa- "Czepaon Airfoils"- ModelAirplaneNews,August,Septembe_-lg57 _
-76-
O0000002-TSG02
(C) .LOWREYNOLDSNUMBER_A]RFOILDESIGN
Until quite recently, the design of _trfotls for Reynolds numbersbelow
about 1 x 106 has been primarily empirical tn nature, guided by observa-
tions of nature's solutions for insects, birds, and small fish, and
. aided by inputs from low Reynolds number smoketunnel flow visualization
and force measurements, In the early years, considerable o_timtsm was
generated by the beneficial effect of tunnel turbulence level in artificially
raising the critical Reynolds number of airfoils which operate well at
increased RN but have very low performance in frea flight at the true
value of lower Reynolds numbers, The brilliant pioneering effort of
Schmttz (reference IV-4) introduced realism tO the game. Technical
aeromodellers, armed wtth the Schmttz results, now began an empirical /
development which, due to their competitive spirit and keen powers of !Jobservation led to some remarkably good atrfo!ls which work well in the !
real world of free fltght at low Reynolds numbers in the earth's atmosphere.
The question nowarises as to whether the present]y available powerful
analytical atrfo_l design procedures can lead to dramatic additional
improvements ove_ the present empirical state of the art as had occurred ................
in the Reynold_ .,_._ur range of 1 x 106 to 3 x 106,
Systematic series of aircraft airfoils were originally designed by NASA
by wrapping the best thickness falrtngs about the best camber lines where
both had comefrom long years of empirical experience. This work of the
20's and 30's was followed in the late 30's by the development of laminar.
airfoils with improved favorable pressure distributions forward of more
aft minimum pressure points and improved linear pressure recoveries aft
of minimumpressure through rear surface cusptng, See Reference IV-A,
These airfoils were excellent at Reynolds numbers above 4 x 106 but
often gave disappointing results at RN's of 0.7 x 106 to 2,5 x 106.
The performance in this regime was remarkably improved by the efforts
of Wortmann, Reference IV-J, and Eppler, Refel_nce IV_, and together
with smooth, wave-free composite construction led to large improvements
in the performance of man-carrying high performance sailplanes for the
past 25 years, (To date, these advantages have been avoided by all but
=i a few Europeanpower plane buildersand some Americanhon_bullders,i
ii -77-
I H " _1
00000002-TSG03
The brl111ant appllcatlon by Llebeck (Reference IV-K), of the Stratford
(Reference IV-B) concavepressure recovery led to drag reduction andltft increases at RN= 1 x 106 to.a level previously thought to be
impossible.
Meanwhile,technical aeromodellers continued to design tmprovedairfoils
' for 20,000 < RN< 300,000 ustng empirical guidance from the few lowturbulence low RNtests available, andchecking every step of the way
with what workedtn the real world of free fllght contests. See
ReferencesIV-C, D, E, F, G, H, 0 and IV-51.
In 1972, Mtley investigated the theoretical lower ltmtt of Reynold_numberfor which the Wortmann,Stratford, and Ltebeck techniques might
apply and set a lower limit of Rc = 300,000. Heconductedtests of the
Hiley H0-6-128 atrfotl designedaccording to theory in the free atmospherenlountedon a sailplane with excellent comparisonwith theory at Rc = 600_000.
To date only R. Eppler and W. H. Phillips have attempted to predict the
of airfoils at Reynoldsnumbersless than 300,000. tlift-dragpolars
TheyhavebothusedtheEppler_thod IV_ and IV-R. Resultsmay he found!
in IV-T,IV-U,andAeromodellerBook (9). Thecalculationsceaseupon
separation.TO datethecalculationshavenotbeeniteratedfor the
boundarylayerdisplacementthicknessnor is thereyet provisionfor
including th_ effects of _ separation bubble with reattachment.Comparisonof tn=ury and experiment for the Eppler 387 is seen in Figure
= IV-5to be quitegoodat Rc = 200,000but furtherin errorat Rc = I00,000.
a An excellentreviewof theprospectsfor theapplicationof modern
airfoildesigntechnologyto the lowReynoldsnumberregimewas provided
m_ by Russell in 1975, ReferenceIV-P, andclearlypointsout theproblems- associated wtth separation. He suggestedthat the exact solution of
I NavlerStokesequationsas appliedby Lalne,ReferenceIII-23,in_ 1972 to the flow over an aft facing step on a plate could eventually
be applied"tothelow RN airfoilproblem.Sincethe computerrequire-mentsareso formidable,it is morelikelythattheapproachof ;!
Venkates_oriuandMarsden,ReferenceIII-30,will be attemptedfirst, i)l
-78-
k '
00000002-TSG04
ORIGINAL PAGE ISOF POOR QUALITY
A
1 ITca I .....
l ...... -- :..T"-- ........................
Theorellsche Polaren ..... ., ._, "_"
I : T_-1-1 ...................... _ ""P,_,,,_307 -I .,'-_<-_'_"="-
I'i_ i ..........................._;Joo-To:---/- ' _..........J ._ l--_*.........
,,o...... . _' ._..,oooo°_ •'--.-............ -_ _-................ .. :'.'2_ _
..................... -/- ..................7 _-...... _..,::I,.......... __
_P,//__f: / .
"--I .... _ ................ _t .............. /- ...... T---_' lenzdruht --"/__j mlt Tuvbu- :,ii
i , " I j i ........ "f
___ _"._\ - ,,,__
, I , , 1....5 10 1$ 20 I000 CW
Verg|uJch dot theoretzschen Poloren mit dun in Dolftgeme_senen Poloron
-J
:JF
FIGURE IV*5
The Eppler type calculations seem to be fastest, and equally accurat_
when comparedwith others at RN_=IO6, Someaspects of the methods gtven
in IV-M,N, q and S may constituteadditionalrefinements. The most
helpfult_chniquein reducingtime and cost of airfoildesign at RN_IO6
is given in referenceIV_V. The man mu_t definitelybe kept in the loop
to keep from being swampedwith usel_sscomputerprintout.
Recently,McMastersand Henderson,VI-W and IV-X, have been exploringthe
possibilityof extendingtheoreticalairfoildevelopmentto lower Reynolds
numbers. It is highly likelythat significantimprovementswill evolve
from this talentedteam.
At present,sumnerof 1981, John Roncz has been using a modifiedEppler
programto optimizethe designof canardsurfacesfor sailplanesand
sport planel_atchord Reynoldsnumbersdown to 380,000. He also closely
followsthe laminarbubble studiesof Dr. Muellerat Notre Dame, John
is fascinatedwith the entire Reynoldsnumber range and it is his hope
that laminarseparationbubblecharacteristicsderivedfrom the smoke
streamphotographsand measurementsof Muellercan be added to the Eppler
;7 airfoildesignmethodand by keepingthe man in the loop it may eventually
be possibleto predictanalyticallythe lift curve and lift drag polar
distortionswhich are found experimentallyat 40,000<RN<380,000
It would appearthat the theoreticalairfoildesigncalculationssO nobly
startedby Epplermay soon be refi.nedto allow accuratepredictionsin
the criticalReynoldsnumberrange. It may Just be that when we arrive
there we will have rediscoveredthe better airfoilsalreadyempiEi._a].ly....
developedby the technicalaeromodellers.m:,
J
-80-
...... - ......... "..... _=, " '-:" Z .. II " _1_1_:= "=uS" I" llnl I 1r "
00000002-TSG06
LOW 8EyNOLDSNUMBERAI,RFOILpESI.GN,BIBL_IOGRAPHy
Discussionsof theproblemspeculiarto thedesignof airfoilsin the
crlticalReynoldsnumberregimemay ba foundIn thebookson Technlcal
Aeromodelllng at the endof this secttnn and in the previously citedreferences,
, I'1, 2 II-l, 2, 5, 6, 7, g III-l, 2, 6, 7, 8, 18, 23, 21_
III-27, 28, 29, 30, 31, and 32
IV-5, 6, 7, 9, lO, 11, 12, 13, 14, 15, 18, 19, 26, 27, 28, 29, 30,31, 32, 33, 34
The followlngreferencesaredirectedSpeclflcallyto theactualairfoll
design problem.
IV-A - Abbott, I. H. and von Doenhoff, A. E Theory of W!ngSectionsCopyright 1949. Dover Publication NewYork, NY1959 1
B - Stratford,B. _. - "ThePredictionof Separationof the Turbulent IBoundary ,'_ "La.e.. Journalof FluidMechanicsVol,5 1959 ..
!C - Krouse,d. R. - "Effectof Undercamberon Endurance"ThirdAnnualSymposiumof theNationalFreeF11ghtSociety1970
:e
D - Krouse,J. R. - "Effectof AirfollParameterson FlightDuration"NationalFreeF11ghtSymposium1971
E - Bogart,C. W. - "A NewFamilyof FreeFlightAirfollsfor a11" Occasions"FourthAnnualSymposiumof theNationalFreeFlight
Society 1971
. F - Monson,D, - "SomeAspectsof AirfollGeometry"NationalFreeFlightSymposium1971
G - Monson,D. - "SomeAspectsof AirfollGeometry- PartII" iFifth Annual Free Flight SymposiumReport 1972u
_ H - Krouse, J. R. - "Airfoil LeadingEdgeBluntness, Goodor Bad"!_ Fifth AnnualFree Flight Syhlpostum1972/
_. I - Miley,S. J. - "AnAnalysisof the Designof AlrfollSections: for LowReynoldsNumbers" Mississippi State University_ Dissertation 1972
J - Wortmann,F. X. - "A CritlcalReviewof thePhyslcalAspectsof• AirfollDesignat LowMachNumbers"NASACR-231S1973K - Llebeck,R. H. - "A Classof AirfoilsDesignedfor Highllftin
IncompressibleFlow" Journalof Aircraft,Vol.lO October1973
i!i -81-
00000002-TSG07
IV-L - Eppler, R, - "Direct Calculation of Airfoils FromPressureDistribution" _SA TTF-15,417 1974
M - Bonnet, E andG_ngrt.ch,P. - "Prediction of Atrfotl ReelFluld Characteristics at SubsonicSpeeds" Rockwell InternationalL.A. Dtvtston NA-73-771ApPtl 1974
and Vanderplants, G. N, AnN - Htck_, R. M,, Muman, E.M., - "Assessmentof Atrfotl Oestgnby NunmrtcalOptimization"NASATM-X-30921974
0 _ Bauer, A. B, - "The LomtnarAJrfotl Problem" Nattonal FreeFltght Symposium1975
P - Russell, J. - "Prospects For The Application of ModernAirfoilDesign Technologyto the LowReynoldsNumberFlow Regime"National Free Fltght SymposiumReport 1975
Q - Narramore, J. C., Olander, R, D., and Stearmanj R. O. -"The Devel.opmentof a ComputerAtded Atrfotl DestgnProcedureIncluding Preliminary WindTunnel Experimentson a LowReynoldsNumberHigh Lift Section" AFOSR-TR-76-O5361976
R - Eppler, R. andSomers,D. M. - '_ow SpeedAtrfotl DesignandAnalysts" NASALangley AdvancedTechnologyAirfoil ResearchConferenceMarch7'9, 1978
S - Kennedy,J. L. and Marsden,D. J. - "A Potential FlowDesignMethodfor MultlcomponentAirfoilSections"JournalofAircraft,Vol.15,No. 1 January1978jpp 47-52
T - Eppler,R. - "SomeNewAirfoils"NASAConferenceon the ScienceandTechnologyo@ Low Speedand MotOrlessFlight March29-30,1979
U - PhIIllps,W. H. - "EpplerCalculationsof the Polarsfor SeveralChamplneModelAirfoils"PrivateCommunicationMarch1979
V - Narramore,J. C. and Yeary,R. D. - "AnAirfoilDesignandAnalysisMethodologyUsingthe InfOrmationSystemsApproach"Bell Helicopter Textron Report, Fort Worth, Texas 1979
W- Henderson,M. L. - "Inverse BoundaryLayer TechniqueFor AtrfotlDesign".NASAAdvancedTechnologyAirfo11Research,Vol.I,NASACP-204B,1978
X - McMasters, J. H. and Henderson,M. L. - "LowSpeedSingleElementAtrfotl Synthesis". NASAConferencePublication2085, Part 1, Science andTechnologyof LowSpeedandHotorless Flight. Hamp'-_, VA. March29-30, 1979
; -82-L
: "-_" -_'L_.l_ :'" """ _ "' _' _ .... ...... '
..... 00000002-TSG08
LOW REYNOLDSNUMBERAIRFOILDESIGNBIBLIOGRAPHY (continued)
IV-Y Galloway,C. R. _ "Applicationof AdvancedAirfoilsto HlghAltitudeLong EnduranceRemotelyPolotedVBhicle_'AlrFareFlightDynamicsLab. ReportTM-77-10-FXM,December1976
IV_Z Llebeck,R. H. -"Superlift AirfoilDevelopmentProgram" iAlr Force FlightDynamicsLab ReportTR_76-110,October 1975
IVoAA Eck, B. - "EverythingYou Ever Wanted to Know About 50B Fins"Tank Talk, 1691B HerfardRoad, Monkton,MD 21111,January1979 I!
IV-BB Safer, F. G. -"SupercriticalAirfoilSectionswith Slotless I_FowlerFlap_ for Glidersand Motorgliders" TechnicalSoaring,Vol. VI, No. I, SeptemberI980
IV-CC Cgglest()n,B. and Surry, D. - "The Povelopmentof Now A-2 AirfoilsAided by Computer" 1980 NationalFree l'lightSympOsiumRepor_
IV-I)DDraisey,S. - "OptimizedAirfoilsat Low ReynoldsNumbers"Universityof WesternOntarioFacultyof EngineeringScience.DegreeThesi.s,March 1978
IV-EE McMasters,J. H., Norovik,R. H., Henderson,M. L. andSandvig,J. H. - "Two AirfoilSectionsDesignedfor Low
ReynoldsNumbers" TechnicalSoaritlg,Vol. VI, No. 4, June !.;1981. Publishedby the SoaringSociety of America
IV-FF Roncz,J. - "Low ReynoldsNumberAirfoilsDerivedby theModifiedEppler Program: Unpublishedto date. Private _,communicatior_,July-August1981
-_3-
......... -.... " - ............. '""' ' _ " ;:" ' " ..... " "-lit " - ....
00000002-TSG09
(D) BOOKSONTECHNICALAEROIVJODELLING
(1) Zatc, F. -Model Aeronautic_Y_arbOpk1936.36,_37, 3B, _"_-!;2_-133,BB;.56,57-5B, 59-61, 74-Ei5ModelAeronautic Publications, Box13B, Northrtdge, Caltf,
(2) Grant, C, H. - "ModelAirplane Dostgn, Theoryof Flight- 1941"Notice in Free Flight _;octety DtOes_for December1974 that ttts to be republished
(3) Schmttz, F, W, - Aer()d.ynamtcsot' the Mode!.Airplane -. 194.2Part 1 - AtrfoT1"_e_Suremeh-ts- Transl at lOfl-byRddst-o-neArsenal,November22, 1967- Originally Published Gotting_,, 194P.
(4) Zatc, F. -Model Gltder Design- 1944ModelA_rona'uti¢Pub_lca_l'ons, Box 135, Northrtdge, Callf,
(5) Hoffman, R. Jo - ModelAeronauticsMadePathless - 1955_del Aeronautlc PubllcatlOnS,-Box135, NorthPtdge, Caltf.
(6) ZatcD F. -Ctrcular Atj'flow - 1964ModelAeronautic PUblications, Box135, Northrtdge, Calif.
(7) Malktno O. -_r, fotl sections (For ModelAirplanes)UpperHurt, NewZealand May1971
(8) Dalb¥, E. andCusick, C. - Bookof.Air.%tlsF.A.I. Model Supply - Phoenlx, Arlzone--85068
(9) Eppler, R. - Mode)-Techptk-BeraterIdTB-1 Eppler ProflleMTB-2 G.oBseglerr.- Hochltestungessegler- Spectal- FlugmodelleVerlag fiJr techntk undHandworkA&BLederthetlBaden-Baden,Germany1977
(10) Pressnel, M. -Aerofoils for AeromodellersPttmanPublishing Corp'.Fearon Pub. In(_. 6 Davts DriveBelmont_Calif. 94002 USA1977
(11) Sl_ns, M, - Hodel Aircraft Aerodynamics3 Model& Allied Publlcatlons - ArgusBooksLimited
14 St JamesRoad,Watford, Hefts, England1978
(12) Althaus,D. - Profilop_o]a_renFb'rDenModellflug.._ N V Neckar- Ve¥1ag'ag--V'S--_V--V-lTITngen- Scl_wenningun1980
(13) Musil,M. - AerodynamikaModernichLeteckychModel_=. NaseVojsko- Praha_19'7-8
(14) Althaus,D. andWortmann,F.X. StuttgarterProfilkatalog!F. Vieweg& Sohn. Wiesbaden; _e-st_Germanyig_'l
(15) NationalFreeFlightSocietyAnnualSymposiumReports- Ig68through19Bl. Can be obtainedfromFredTerzian,4858MooreparkAvenue,San Jose,CA 95129
-84-
00000002-TSG10
V, BOUNDARYI,AYFR TRIPI'INt; DI':V[CI'S
A, t-Ilstorl.cal review
The pionoorlng l¢_w Roynolds numh_r tnvosttgntY_ons of Sehmttz
(Roforonee lV-4] lncludod tt_._ts In which the porfarmanao of th_"} no
.,,, thick 6B 625 W_l:_llIarkodly improvod at Rc=82,000 hy ti turlml_meo
wire pla_eed ahond of tilt: loading c,dgo, _h_Llar It_rgo porformance
lml_rovon_ont:_ wt_ro oht_ttnod lit Re_I_II,(IIIIIwith a w:tr_, grid placedahotld ot' tho illodol,
AIt_o In tilt, l_),lilttl, I'l'ollllingqr (ltot'orqne¢, IVoS} Invq;_ttgatqd tho
eft'oct o|' aft flwlng ;_op. _, In _hq Ul_pOr ,_m'faco, ._u_t'a¢o wuvlno;f:_,
l_ml _i:lr ,Iot:_ blt_whlg _;hro_t_h the UplX,r mwt;aeq _i" lnm l:llir tiIrfoll._
|'t)P I{e)'noldt_ nttll|bt, r,q o1" 250,(1111) to 1 x lil (_, lie lil._o noted tho
reduction In drag :it high lift coefflclqnt at subcrtttcal airfoil- (1IRt:yll_,lds IIttlllbqr conabinations, All of the._e devices ¢lltl_O early
enough boundary layer trans|tion to allow bottndary layer roattachment
forw/trd ot r tile trail:log edge. The lower the, Reynolds number, the
t'ltrther forward nut,_t lilt' trip device be located to ensure reattach..
meat forward of tile trat l|ng t;dge.
The rest:arch be_;un by Schmitz was continued IW _'r_wmer including the
effect',_ of trip wires (Reference IV-13). Pfenninger (Ruferences
lV-ll, 1V-32) inw, stigated multiple surface mounted boundary layer
tri.ps on a thin airfoil down to Rc_21,I)O0. Bounda_'y layer tripping
was also inclttded in a_rfoil tests by Phillips (IV-26), Volkers
(tV-2_], tlendricks t 1V-24), anJ Eggleston (1V-27 and IV-C(1). Hacklinger
has stt_d_ed the effect of trips in free flight (IV-55 and IV-71).
Nost recently, addit_tmal data ts available from the low turbulence wind
tunnels at Delft (IV-36) and at Stuttgart (IV-47) trips were used on
a large number of airfoils.
The only atte!npt to evaluate the relative advantages of various types
;: of surface trips was the study of Shoal, Reference V-1.17
i •
-85-
00000002-TSG 1
B, Various Mothoda of Boundary Layer Tripping, (See Figure V-l),
l, Increase tl_e free stream turbulence by placing a wire or grid
of wtros in tht_ flow ahet/d of the wtn/_.
2, Beam sound energ), at the t'orwurd upper wing surface with a
fv'oquoncy calculated to be most crttlcnl J_t the test tte),n_lds
lllllllbOr,
3, VllJri:tlngthe wln_,nt ¢rltl_'alfr¢,qm.lcy,
,I, llulldlI1gwavo,_of crltl,_:,alwnvo lowlgthIntt_the .plmr wl1_g,_urfl.'o,
' !.g, III_0of lll'tl'ill_lll_,qtOll:l Ill the IlPllOl'wlpt, Slll_fIll'O,
o. llondl1_l;oI'multlplo ,_qmtiwl,_onnmlng t:ap_:_to the lqq_ol'wln_;
illlr|'Ii¢o,
7 One or ,lore spanwt.qo running wlrq,g o1' strtp,_ bolldod to the upper
wI nt,, surface.
8 A spanwlso row of small rtl,ht crtcular ,:yl indors bond_d to tl_e
tripper wing stir{ace.
9 A Sl)anw;se running strip of IlUlltil'Jlo spherical beads bonded .:o
tile Ul_per wing stlrFaco.
10 A sp'mwtse run,lit_g raised or recessed st, rrated strip {llama :;trip]
bonded to tile upper wtttg surface..i
11 A spanwise row of holes through the wing allowing air jets to
blow uut normal to the upper sul'face.i
12 A sharp leading edge at high anglo of attack.
13, Normal sections at high angle of attack and low Reynolds number
often automatically provide early enough transition to avoid 't
the, non-reattachment problem. ,,
It would be desirable to know which type of boundary layer trigptng would
be Ol_timum for any given Reynolds number. It i.: known that:i
I. laminar separation bubbles are small enough at chord ,,t
V:N > ,lxlO (_ to Ii|.tke art it'tcial tripping tlnnecesstlry. !
2. It soeltls very dlft'ic.ult and perhaps illlpos._ible to effectively
prevent non-reatt(tched separ, ted flow at lift coefficient
.tl.8 at chord RN ;! lO,t_O0.
i: -86-
00000002-TSG32
ORIGINALPAGE18oFpoorquALm'
._, At 300,000 < RC < 4xlO fi, the instability gradient a_ a tripping
device 1V-,! seems to Im an excellent method af limiting the
adverse effects of laminar sop_lrntian lmllbles,
.I, Far II)O,IIII(I ¢ i1¢ < 5[Ifl,/IflII, surt'a¢o wavlnvss, and aft fac|ng
steps are helpfill tellq_i.ng devtzos [TV-5],
5, A tt'ip wire lOq, chard tlhfuld nf wing lemllng edge Improvoae
_Irl'ollI,II__ttlilhlltloli_rii_low _._ ,i(J,ll(|i},
t,, M tlm I!t79Intt,rnlttlonall:vooFlight Model Alrfail Moot, tho :I1
IIIfD!'d pl't'Vll|i'llt l)'po of h,1, trlplu,r wii,i tl initiate crot_;4-_q¢1ion i
,_i}Jllll_t_fi_.,rllllIlilU _,vldw.,, L,Itlwv !tlll_IIo ur two Ill t_orlo,_, 'rlwt_t, !Wol'O |'Olllld Oll thq |'Ol'Wlll'd Ilppt, r ._tlri'lwot& of wlll_U_, horl_o_l_Jl
trill., lilld I_ropoller_, IliO:_t of w)llfh wqrt, Ol_el'litlll}i lit tl I{N range
of ;,.O,O(!l}to 7(},000, I did not r;e_,3odlmtqmlomll trlpg such a.q
_ t'owof pln._or'a ._telpof _,,m_tllb,.,ad_.The Israt,ll team hml
the lllmqt.qol_hl._tlcatedtl'ip. It w:t,.,a reve.q,qedllamastrlp on
the l'm'wardUl_l_t,rwi,g sm'l'act,,'l'herear edge was flush with
the wing, 'l'hvwing ._teppeddown to a thlnne_'leading pot'tion
ab_'tq_tly,The face oF tlw l'm'wardl'acingstt,p was saw-toothed
In plan form, thtt.q prodttc!ng a theee dimensional dtstttrbanee
to the boundary layel'.
7, With the exception of ShoaF's p'tpe.', V-l, the writer has not
seen comparative quantitative data on various t.vpes of b.1.
t rippers.
DI St,llSS 1( N =C. '' " ]q
1. Two Dimensional Tcip Strip on Forward Upper Surface - Stuttgart I
Data
Two dimensional airfoil mounted trip strips were employed in
some of the Stttttgart measurements. Trips appear on three
airfoils at R = 40,000, ntne airfoils at 60,000, and tenc_,it'foils at 100,000 R .¢
1-88- !
• .),
_" .'-'_" ., " '_' -"'.:::-,_ _'_ .-__._" "_ " "_L .......... !. : ._ ",F" , .: ...... :....... L_ , ,_.... ? - , _ - :, .'_._. .:.'_ ,_...__.'__".. '_'.__'__!.._
00000002-TSG]4
AirfOil Trip Location Trip Height Trlp Width ', , .......... ,,, .; ............. • .......... ,--. 7
FX 60.100 0,20 X/C 0,3 mm 2 mm
FX 60-126 0,10 0,3 mm ..... 2 mm
FX 63-137 0.20 0.3 mm 2 mm
FX 62-K 131/17 0.205 0.3 nun 2 nun
FX M-2 0.030 0.3 mm 2 H
_t 79-100B 0,0625 0,45 mm 2 nun
AH 79-_OOB 0,0875 0.3 mm 2 nun
AH 79-100C 0.23 0.5 mm S
B-193 0.10 0.3 mm 2
E-193 0.23 0.3 mm 2
E-203 0.083 O. 15 nun 2 mm
Sokolov 0.092 O. 3 mm 2 n_
..... J .....
In general, a performance improvement and a reduction in polar
and lift curve distortion wlll result from tripping an airfoil
at Reynolds number lower than the critical value for the bare
airfoil. Pcrfo_nance decrements are gonerally found when trips
are-_etained on airfoils at Reynolds numbers greater than the
. b_re airfoil critical. The effect of .012 inch high by .08 inch
wide rectangular cross sectioned upper surface trips located at
.03 <_ " "3 on (L/D) max is shown in Table I, the effect on
• iS shown in Table 2, and the effect on polar and
rms appear in Table 3. The performances of all Ii
. improved at Rc = 40,000, the performance of 55%
were improved at Rc = 60,000, and the performance of 33% were
_mproved at Rc = 100,000. The effect of the trip on the FX 63-137
at 60,000 was very dramatic, bringing an airfoil which sim_ly
could not be used at that Reynolds number up to quite a commend-
,_ble performance.
A somewhat unusual result was the effect of the trip at 100,000
Rc improving the AH-100C from a Incdiumperformance to top perform-
ance. Thc trip improved the polar and llft curve forms for the
. -eg- C -
00000003
i
t¢
TAB!,E I - Tit[P I_FI,I!{;T ON (_.X
AIR FOIl, Rc - 40,0ll0 I It - 60,000 Ite - 100,000,
- mi+_,_J.... vi+ri,+_i:_-i+-_,.... 'rrq, -Si+ar+TC++-"i
--++_"" + - "I
M=2 17 29 20 I 37 46,5 48.6 ,
E- l,q3 26 30 38 i 38 47.5 41I
Sokolnv 31,6 35 34 45.5 61 58
!;X63- 137 8.2! 40 46 43
FX60_ 126 30 [ 37.5 52 50
FXbO-100 32 I 38 $9 49E-203 40 36.5 45 46
I
i All IOOB 40 39 5.5 50
All ]OOC I 38 t 38 .54 6.5
+ZK,tSt/t7 tO°f_ S2 4_1K131/17 15°_ 42 43
TABI,E2 - TRIP I'FI'+ECTON (I3/2/I))MAX
AIR FOIl, R 401000 R - 60,000 R = lO0,OOOC C ,C
Baro'l T'rip 'Bare l;l'[p _ Bare Trip
M-2 13 23 23 37 38 48
E-193 ..... 28 • 30 49 40 49 42.2
Sokolov 37..5 39 52 53 70.5 67FX63-137 5.4 45 51 49
FXOO-I2b 33 37 .53 42
FXO0-100 33 - 32 58 46
E-203 42 38 50 43
All IOOB 47 45 _2 5b
_1 lOOC 38 4_-. 5_ 70 "
62K131]17 10°_ .59.3 54
62K131/17 15°6 Li ................. [__+. ,t9 48
-90-t
iI
00000003-TSA03
-91 =I) i
I
...... '. ,' -'-" " " "" ....._ ..... h,,_," - " .........._ ' ')" ...... r t " .,"'_---. 7 ..
00000003-TSA04
FX 62K 131/17 with deflected flap at a small decr_me.L in (L/D)
max and (L3/2/D) max at Re - i00,000, D_tailed comparison of bare
and tripped palate and llft ourves should provlde addi£1onal
insight on optimum use of boundary layer trips.
'Pile effect of 0•5% chord diameter wi_e located 2% chord above the
chord line and I0% chord in front of the loading edge on the polar
and lif_ curve at Re - 80,000 and 50,000 i_ Bhown in Figures V-2
and V-3• The wire completely removes the large drag increase at
medium lift coefficients and takes the sag out of the lift curve,
An appreciable loss in (L/D) max and L3/2/D results. It is
unfortunate we do not have data on the E-61 with an upper surface trip.
(c) Effect of Beamed Sound Pressure--Delft Data
The beneficial effect of beamed 105 db 300 cycle sound at Rc - 80,000
is shown in Figure V-2 and the effect of 104 db 145 cycle sound at
R ffi50,000 is shown in Figure V-3 The remoeal of the drag increase I'C • ..........
at medium llf_ coefficleats an& removal of llft-curve "sag" are now
obtained with less dost in (L/D) max and (L3/2/D) max if one does not
consider the drag equivalent of the power required to produce the
noise• Tile effect of the sound.pressure level in db at optlmttm
frequency on the llft coefficient in the "sag" region is shown ini
Figure V-4. Note that the sound level in the Delft tunnel is 74 dbi
without the tuned noise maker• This d_a.pelnts out once more the ii
complexity of the aerodynamics of airfoils in the critical Reynolds 1
number range so nobly pioneered by Schmltz and Pfennlnger.
-92-
00000003-TSA05
00000003-TSA07
(D) BoundaryLayer Tripping.Bibliography
Discussions of and in manycases data from boundarylayer tripping
experimentsmayba found in references; IV-4, IV-5, IV-B, IV-l.1,
IV-13,IV-P.2,IV-24,IV-26,IV-27,IV-29,IV-30,IV-31,IV-32,IV-36,
IV-43,IV-47,IV-4B,IV-4g,IV-55,IV-71,IV-72,IV-73,and in the
booksIV-3-1,3, 10, 11,12, 13,15,as woilas in:
V-I Sheaf,H.C.- Characteristicsof TurbulatedAirfoils,
ZaicIg64-65Yearbook.
V-2 Hacklinger_M. - ArtificialTurbulence,Zaic1955-56Yearbook.
V-3 Christi,C.M.- TurbulentFlowAirfoils,Zaic1955-56Yearbook.
V-4 Gillesple,W. - RubberPower& Turbulators,Zaic1gS7-58Yearbook.
V-5 Baxter,D. - RubberPower& Turbulators,Zaic1957-58Yearbook.
V-6 Pearce,F. - AirfoilTurbulators,Zaic195g-61Yearbook.
V-7 McBaine,C.K.- Letteron MultiStringerTurbulator.
Zaic!959-61Yearbook
V-8 Neustein,J. - Experimentsat LowReynoldsNumberS.
PartI - IsolatedAirfoils.Cal TechReportNo. 6, March,1957.
-96-
..._.,,_,JL::.zL_ _ "" .-' .... *, , ,,,i,, "
00000003-TSA09
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