Wake instability issues: from circular cylinders, stalled ... · Motivation Secondary Instabilities in the Wake Two circular cylinders in tandem Stalled airfoil VIN: ... Iago Barbeiro,

Motivation Secondary Instabilities in the Wake Two circular cylinders in tandem Stalled airfoil VIN: High lift device Fapesp/BG Gas Innovation Centre Conclusions Acknowledgments

Wake instability issues: from circular cylinders, stalled airfoilsto flow control

Julio R. Meneghini, José A.P. Aranha, Clóvis A. Martins, Bruno S. Carmo,Gustavo R.S. Ássi, Ernani V. Volpe, Rafael S. Gioria, Gustavo Patino,

Douglas Serson, Ivan Korkiscko, Stergios P. Tsiloufas, André S. Bonatto,Iago Barbeiro, Adson A. Paula, Reinaldo Orselli,

“Núcleo de Dinâmica e Fluidos-NDF”, POLIFluids and Dynamics Research Group - NDF University of São Paulo - Brazil

Fapesp California Week November 17-21 November 2014

Meneghini et al. (2013) University of São Paulo, Brazil 18-11-2014 1 / 60


Outline1 Motivation

Building a concrete knowledge: “from the possible to the necessary"Recent PublicationsVortex-induced vibration (VIV) on risersAirplanesSome previous work

2 Secondary Instabilities in the WakeThe meaning of secondary instabilityFloquet analysis: FundamentalsIsolated circular cylinder

3 Two circular cylinders in tandemDefining parametersPrevious studies of two circular cylinders in tandemSecondary instability for two circular cylinders in tandem

4 Stalled airfoilPeriodic base flowStability analysis

5 VIN: High lift device6 Fapesp/BG Gas Innovation Centre7 Conclusions



Building a concrete knowledge: “from the possible to the necessary":NDF Infra-structure



Some recent "publications"



Building a concrete knowledge: Some recent publications



Wake-induced Vibration (WIV) and Wake Stiffness Concepts



Wake-induced Vibration (WIV) and Wake Stiffness Concepts



Building a concrete knowledge: Some recent publications



Moving Boundary Surface Concept for VIV Suppressor and DragAttenuator



Moving Boundary Surface Concept for VIV Suppressor and DragAttenuator



Motivation 1: VIV on risers



Motivation 2: Airplanes and Vortex-induced noise (VIN)



Reality is a bit different...



Meneghini, Saltara, Siqueira and Ferrari Jr. (Journal of Fluids &Structures 2001









Outline1 Motivation








What do we mean by secondary instability?

The primary instability is the onset of vortex shedding for Re ' 48 whichbreaks the symmetry in relation to wake centreline.The secondary instabilities occour for Re > 188 and are characterized bythe lost of the spanwise symmetry: the wake becomesthree-dimmensional.Modes A and B are observed in the range 180 < Re < 300 (Williamson1996).



Fixed circular cylinder: 2d and 3d wakes

2d wakeRe = 110

Mode A,typical wavelenght ⇡ 4.0D

Re ⇡ 190

Mode B,typical wavelenght ⇡ 0.8D

Re ⇡ 270

Quasi-periodic mode also possible at higher Reynolds (⇡ 370).

Figures adapted from Williamson (1988).



Secondary Stability Analysis methodology: Summary

u is T -periodic

u(x , y , z, t0)e�t0 after T :u(x , y , z, t0 + T )e�(t0+T ) = u(x , y , z, t0 + T )e�t0

e

�T

Floquet multiplier: µ ⌘ e

�T

Stability criterion:|µ| 1: solution is stable|µ| > 1: solution is unstable

Fourier expansion in the spanwise direction as the system ishomogeneous in this direction:

u0(x , y , z, t) =

Z 1

�1

_u(x , y ,�, t)ei�z

d�

A set of two dimensional problems with Re and � as parametersArnoldi method is used to compute the Floquet multipliers of largestmagnitude



Isolated circular cylinder: Floquet multiplier versus � curve



Isolated circular cylinder: neutral stability curves



Isolated circular cylinder: neutral stability curves

Figures adapted Henderson (1997) and Williamson (1996).



Isolated Cylinder: Modes A and B Symmetries

Mode A

!x

(x , y , z, t) = �!x

(x ,�y , z, t + T/2)

Mode B

!x

(x , y , z, t) = !x

(x ,�y , z, t + T/2)



Isolated circular cylinder: Modes A and B, non-linear analysis

Figures adapted Henderson (1997).



Outline1 Motivation








What happens when two cylinders are arranged in a tandemconfiguration?

Meneghini et al.(2001), Carmo & Meneghini (2006) and Carmo et al.(2010).



Secondary instability for two circular cylinders in tandem

The results are presented according to the vortex-shedding regime

Regime SG

L

x

/D = 1.5

Regime AG

L

x

/D = 1.8 and L

x

/D = 2.3

Regime WG, L

x

/D = 5

From Carmo et al.(2010).Meneghini et al. (2013) University of São Paulo, Brazil 18-11-2014 28 / 60


Regime SG, L

x

/D = 1.5: Floquet stability analysis



Regime SG, L

x

/D = 1.5: Unsteable mode



Regime SG, L

x

/D = 1.5: Non-linear analysis



Regime AG, L

x

/D = 2.3: Floquet stability analysis



Regime AG, L

x

/D = 2.3: Unsteable mode



Regime AG, L

x

/D = 2.3: Physical mechanism



Regime AG, L

x

/D = 2.3: Non-linear analysis



Regime WG, L

x

/D = 5: Floquet stability analysis



Regime WG, L

x

/D = 5: Unsteable mode



Regime WG, L

x

/D = 5: Non-linear analysis



Regime WG, L

x

/D = 5: Saturated state



Two cylinders in tandem: Summary

Different unstable modes forsmall L

x

/D, but all of them haveRecr higher than that for anisolated cylinder.For large L

x

/D (regime WG), thesecondary instability isqualitatively the same as for anisolated cylinder.



Outline1 Motivation








Periodic base flow: NACA0012, ↵ = 200



Stability analysis: NACA0012, ↵ = 200

1,0|μ|

Re 400 Re 450 Re 460 Re 470 Re 500 Re 550 Re 600 Re 650

0,0

0 5 10 15 20β∙c



Neutral stability curves: NACA0012, ↵ = 200

0.00.51.01.52.02.53.0

450 500 550 600 650

ë/c

ReSub-harmonic mode

Quasi-periodic mode



Reconstructed flow: NACA0012, ↵ = 200

(a) Reconstructed three-dimensional fow. (b) Results from DNS calculations.Translucent surfaces are iso-surfaces of !

z

. Solid dark and light surfaces areiso-surfaces of !

x

. NACA 0012, Re = 500, ↵ = 200, � = 11.



Reconstructed flow: NACA0012, Re = 500, ↵ = 200



Stability analysis: NACA0012, ↵ = 200

Instant contours of !x

. (a) Position of the station for data acquisition inx = 1.5c. Continuous and dashed lines show values of !

z

equal to �2 and 2.(b) Contours of !

x

for x = 1.5c as function of time.



Reconstructed flow: NACA0012, ↵ = 200

Reconstructed three-dimensional fow. Translucent surfaces are iso-surfacesof !

z

. Solid dark and light surfaces are iso-surfaces of !x

. NACA 0012,Re = 590, ↵ = 200, � = 3.



Reconstructed flow: NACA0012, Re = 585, ↵ = 200



Airfoil NACA0012 ↵ = 200: Non-linear analysis, Re = 500

(a) Growth and saturation of the three-dimensional perturbation amplitude. Inblack results for quasi-three-dimensional simulations, in black the Landau

equation, in red the result for Floquet linear analysis. (b) Derivative ofamplitude logarithm versus square amplitude. + Numerical results.



Airfoil NACA0012 ↵ = 200: Non-linear analysis, Re = 585

NACA 0012, Re = 585, ↵ = 200. (a) Evolution of amplitude of perturbationwith wavelength L = (2⇡/3)c = 2.09c. (b) Evolution of amplitude of

perturbation with wavelength L/3 = (2⇡/9)c = 0.70c.



Outline1 Motivation








High lift device: Slat, 30P30N, Re = 1.7 million

Vorticity countors

2D simulations, SST turbulence model with source terms switched off at the region, mesh with 484919 elements, �t = 10�7secs, �ta1/c = 7.2 ⇥ 10�5 ,

Bonatto et al.(2010).



High lift device: Slat, 30P30N, Re = 1.7 million

Pressure field and accoustic wave propagation

2D simulations, SST turbulence model with source terms switched off at the region, mesh with 484919 elements, �t = 10�7secs, �ta1/c = 7.2 ⇥ 10�5 ,

Bonatto et al.(2010).



Outline1 Motivation








Research, Innovation and Dissemination Centers (RIDC)Host Institution: "Escola Politécnica - USP" - University of São PauloAssociate Institutions:

Instituto de Energia e Ambiente (IEE)Instituto de Pesquisas Energéticas e Nucleares (IPEN) Escola deEngenharia Mauá (EEM)

Associate Institutions Abroad:Imperial College LondonUniversity College LondonUniversity of Illinois at Urbana-ChampaignUniversity of CambridgeTexas A&M UniversityTechnische Universitaet Darmstadt - GermanyUniversity of Leeds, UKUniversity of Lyon, France



Fapesp/BG Gas Innovation Centre

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Joint!Steering!Committee!Representatives!from!

FAPESP,!BG!Brasil!and!SGI!

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Executive!Committee!!

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)TT!Manager!

Education)&)Knowledge)Diffusion!

Coordination)EKD!Manager!

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Engineering)Research)Programme)!

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Project)Coordinators:)!!

Prof.!Dr.!Claudio!Augusto!Oller!do!Nascimento!(PoliDUSP)!

Prof.!Dr.!Elisabete!Moreira!Assaf!!(IQSCDUSP)!

Prof.!Dr.!Guenther!Carlos!Krieger!Filho!(PoliDUSP)!

Prof.!Dr.!José!Mansur!Assaf!(UFSCar)!!Prof.!Dr.!Jose!Carlos!Mierzwa!(PoliDUSP)!!Prof.!Dr.!José!Roberto!Simões!Moreira!

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Prof.!Dr.!Alberto!H.!Neto!Prof.!Dr.!Fernando!Facury!Scaff!!

(Law!CollegeDUSP)!Prof.!Dr.!Gilberto!Bercovici!!

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(IEE–USP)!Prof.!Dr.!Alberto!J.!Fossa!!(ABRINSTAL)!

Prof.!Dr.!Murilo!Tadeu!W.!Fagá!!!(IEE–USP)!

Prof.!Dr.!Marcelo!de!Andrade!Romero!!(FAU–USP)!

Prof.!Dr.!Rodrigo!Galbieri!(IEEDUSP)!Profa.!Dra.!Prof.!Virginia!Parente))

(IEE–USP)!Prof.!Dr.!Suani!Teixeira!Coelho!!

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International)Advisory)Board)

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Outline1 Motivation








Conclusions

VIV and VIN Suppressor:MBS is a promising device: could be employed by Petrobras and Embraer

Two circular cylinder in tandem:Very large amplitudes of oscillation in the case of two cylinders in tandem:WAKE-INDUCED VIBRATIONConfigurations in regimes SG and AG: onset of the 3d wake transitionremarkably different from isolated cylinder.Configurations in regime WG: onset of the 3d wake transition similar to thatof an isolated cylinder; quantitative differences in line suggested physicalmechanisms.

Stalled airfoil:Some effects of the symmetry break of the base flow have been shownThe neutral stability curves showed remarkable differences with those fromthe circular cylinder.

Slat and Noise Generation, Flow Control, FAPESP/BG Gas InnovationCentre

A very long way....



Acknowledgments

Sponsors

FAPESPUSPFINEP/CTPetroCNPqCapesPetrobrasEmbraerBG GroupVoith HydroOxitenoBG GroupBP


Documents

Wake instability issues: from circular cylinders, stalled ... · Motivation Secondary Instabilities in the Wake Two circular cylinders in tandem Stalled airfoil VIN: ... Iago Barbeiro,