Hydrod-Prop.pdf

8/10/2019 Hydrod-Prop.pdf

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J. Paulo Vilas-Boas, Ph.D

Full Professor, Olympic Coach, Pres.GA Portuguese Swimming Federation, SG-BMS-WCSS

[email protected]

Hydrodynamics of human swimming propulsion


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VP for C. Educ. Olympic SwimmingCoach

Full Professor

SG-BMS, WCSS

Who I am, andhow do I see myself in swimming ?


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Swimming research and assessment shouldbe relevant for practical swimming purposes!

Myself (also as a biophysicist) in swimming


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Vilas-Boas family


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Hydrodynamicsof swimming

fundamentals for the

understanding ofpropulsion


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TheTheTheThe theorytheorytheorytheory of techniqueof techniqueof techniqueof technique

The rational of the movementThe rational of the movementThe rational of the movementThe rational of the movement


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Hydroynamic propulsion(drag, lift, vortex)

Hydroynamic drag(pressure, friction, wave)


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P + D = m * a

P > D a is positive

P < D a is negativeP = D a = 0 v = const.


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D = CD S v2

W = D . v.

(K = CD S)W = K . v3.

W = E . ep. .

v = E . ep

D

.

.

E Depv

=

W = D .v = E . ep. .

di Prampero et al. (1974)

The swimming technique is it important for the elite swimmer?The swimming technique is it important for the elite swimmer?The swimming technique is it important for the elite swimmer?The swimming technique is it important for the elite swimmer?


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Image based

3D Kinematics (APAS,Peak, SIMI)

+ other kinematics

EMG

Force Plates

dynamometry

Direct

Oxymetry + [La-]

Electronicsdevelopment

Swimming biomechanics (research, evaluation & advice)Swimming physiology (research, evaluation & advice)Swimming psychology (research, evaluation & advice)

Swimming training (research, evaluation & advice)

.0000 5.0000 10.000 15.000 20.000 25.000seconds

-10.0000

-5.00000

0.000005.0000010.0000

mV

EMG

0.000002.000004.000006.000008.0000010.0000

mV

ABS

0.00000

1.00000

2.00000

3.00000

mV

envelope

0.000001.000002.000003.000004.000005.00000

mV/sqrt(s)

RMS

-0.500000.000000.500001.000001.500002.000002.50000

mV.s

iEMG

+

-

Ref.

10cm cabos Holter Pramplificador

16

(2m;4x 0.1mm,7x multicore)

screened;85pF/m;384 /km

18

AD621AN

2 18

35 4

7

+Vss

-Vss

6

150K

+Vss

-Vss

100K

10K17

19

1415

1

2

30

29

Vo

COM

+15V

GND

Policarbonato1 F 5%

AD210BN

[email protected]


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10

20

30

40

50

60

70

80

90100

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E-tot(mlO2/Kg/min)

1.0 m/s 1.2 m/s 1.4 m/s 1.6 m/s

Free

Fly

Breast

Back

Biophysical approaches

N = 26 (8 Fem, 18 Mal)


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P = 0.5P = 0.5P = 0.5P = 0.5 CCCCDDDD S vS vS vS v3333

EC = f (EC = f (EC = f (EC = f (v/cv/cv/cv/c))))

N = 5N = 5N = 5N = 5

3 x 200 (75, 85, 100%)3 x 200 (75, 85, 100%)3 x 200 (75, 85, 100%)3 x 200 (75, 85, 100%)

30 min rest30 min rest30 min rest30 min rest

[email protected]


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Mechanisms forthe production of

hydrodynamicpropulsion


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We dont know exactly how theswimming movements propels the

swimming body through the water,and the complex flow patterns foundin the real conditions make difficult

any mathematical analysis

Gadd (1963, p. 483)


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- theory of non viscous flowover slender bodies

- theory of quasi-static flow


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Static flow (stable flow)

Quasi static flow

Unstable flow (non static flow)


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Propulsive drag theory

Propulsive lift (foil) theory

Propulsive vortex theory

Present theoretical situation:


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Propulsive drag

theory


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Cureton (1930)

Counsilman (1968)


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According to the

propulsive drag theory:

Swimmers propelled themselves throughsuccessive propulsive segmental actions

that intend to push water backwards in

relation to the intended direction for entirebody movement

Theoretical background:

Newton's 3th low of motion (action / reaction)


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(propulsive ) DRAG force Newtonian equation:

DP = Hydrodynamic (propulsive) drag force = water specific mass

CD = drag force coefficient

v = relative velocity

S = Maximal cross-sectional area normal to force direction

DP = 0.5 CD v2

S


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Shoulder / hand

Hand / water Shoulder / water


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Main reasons for

hydrodynamic drag force theorypopularity

(Barthels, 1977)

- The swimmer perceives his movements as backwardoriented movements

- A exterior observer perceives the swimmers movementsas backward oriented movements


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Kinematic references


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Permanent light-trace photographyPhotogrametry Anatomic

markers

(actives)

LEDs & lamps

Vilas-Boas (1993); Vilas-Boas & Ferreira da Silva (1993)


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Vilas-Boas (1993)

Photogrametry

Vilas-Boas & Ferreira da Silva (1993).Anlise cinemtica da tcnica de bruos ondulatrio

com recuperao area dos membros superiores

Alves & Vilas-Boas (1992). Kinematicalanalysis of freestyle hand-path with and

without hand-paddles

Permanent light-tracephotography


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Vilas-Boas et al. (1996). Movement analysis in simultaneous swimming techniques.

FTUDSP

FHUDSP

FIT =FHUDSPFTUDSP

HiTDSP

HiHD

HiIT =HiTDSP

HiHD

HA-PHD

HDHA-PHD

HDIH =

Vilas-Boas & Cunha (1995). Fatigue related technical changes in butterfly swimming.

Photogrametry

Permanent light-tracephotography


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Propulsive lift

(foil) theory


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Counsilman (1971)

Schleihauf (1974, 1979, 1984, 1986)

Schleihauf et al. (1983, 1988)

Wood (1979)Berger (1996)

Berger et al. (1996)


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Basic assumption:

Part, or the totality, of thepropulsive segments are

able to produce a

hydrodynamic forceperpendicular to its

direction of movement

relative to the fluid.


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Lift force:

Defined as a hydrodynamic

force perpendicular to the

bodys direction of motion.


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Bernoulli theorem:

For ideal fluids, there exists aninverse relationship between

velocity and pressure

Magnus effect


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Magnus effect

> V; < P

< V; > P

Schleihauf (1974, 1979, 1984, 1986)


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Schleihauf (1974, 1979, 1984, 1986)

Schleihauf et al. (1983, 1988)Wood (1979)

Berger (1996)

Berger et al. (1996)

The Human hand and forearm are

able to produce hydrodynamic liftforces due to the similarity of its

shapes with a aerofoil shape.


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Production ofhydrodynamic lift

force by a aerofoilshape object


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Thomson theorem:

Into a non-viscous

incompressible flow

submitted to the actionof potential massic

forces, the velocity

circulation along anyclose fluid contour is

constant on time.


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Is hydrodynamic LIFT FORCE the...

...only propulsive force in

swimming?

...main propulsive force inswimming?


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L

Dp

R


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Critics to the foil theory


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Unsteady flowSteady flow vs.

Newton vs. Bernoulli???

y

Evidencies pro-foil


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Propulsive surfaces are notPropulsive surfaces are notPropulsive surfaces are notPropulsive surfaces are not

hydrodynamic neutralhydrodynamic neutralhydrodynamic neutralhydrodynamic neutral

(Berger, 1996)

Presence of tip vortexesPresence of tip vortexesPresence of tip vortexesPresence of tip vortexes

TortuosityTortuosityTortuosityTortuosity of limb movementsof limb movementsof limb movementsof limb movements

and prevalence of vertical andand prevalence of vertical andand prevalence of vertical andand prevalence of vertical and

mediummediummediummedium----lateral displacements.lateral displacements.lateral displacements.lateral displacements.

(Schleihauf, 1979) (Reischle, 1988)


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[email protected]

Marinho, D.A.; Barbosa, T.M.; Reis, V.M.; Kjendlie, P.L.; Alves, F.B.; Vilas-Boas,J P M h d L Sil A J R b A I ( ) S i i l i f


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CFD- Computer Flow DynamicsFluent software

Angle of attack ()

Dragcoefficie

nt

0,1

0,3

0,5

0,7

0,9

1,1

0 15 30 45 60 75 90

Fingers "abertos"

Fingers "semi-

abertos"

Fingers "fechados"

0,1

0,3

0,5

0,7

0 15 30 45 60 75 90

0.64 cm spread

0.32 cm spread

closed

Fingers

Attack angle (degrees)

Angle of attack ()

Liftcoefficient

J.P.; Machado, L.; Silva, A.J.; Rouboa, A.I. (2010). Swimming propulsion forces

are enhanced by a small finger spread. Journal of Applied Biomechanics, 26: 87-92.

Effective hydrodynamic


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y ypropulsive force:

The component on the direction of intended body motion, of

the...

...resultant force (R) of

hydrodynamic propulsive lift (L)

and

hydrodynamic propulsive drag (DP)

forces


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PPPP

LLLL

DpDpDpDp

RRRR

Propulsive segments hydrodynamic configuration:


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Orientation relatively to the flowInclination relatively to the flow

Angle of attack

()

Angle of orientation

- Sweepback - ()

Robert Schleihauf Jr. (1979)


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CL values CD values

Finger positions Tumb positions


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Robert Schleihauf Jr. (1979)


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Toussaint (2002)


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Direction of the successive

phases of the propulsive


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Intensity ofP

p p ppathway of propulsive

segments

Velocity ofsegments

Circumstantialcharacteristicsof segments

Adapted from Vilas-Boas (1986)

direction, orientation, intensityof DP, L and R

The kinetic analysis of swimming techniques showed:


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y g q

Propulsion produced at least from the armsaction is (partly) due to a combination of

propulsive drag and propulsive lift forces.

Circumstantially one or the other of both forcesassumes a more relevant propulsive role.

(Schleihauf, 1974, 1979, 1984, 1986; Wood, 1979; Schleihauf et al.,1983, 1988; Thayer et al., 1986; Berger, 1996; Berger et al., 1996)

These findings do not exclude the contribution of otherpropulsive mechanisms.


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Kolmogorov e Cappaert (sd). Personal repport


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81.3312.09

.3080.061



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Propulsive vortex

theory


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Specially centred into legactions of front crawl,

backstroke and butterfly

Propulsive vortex theory

Lift force paradox for leg kick


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Lift force paradox for leg kicksinusoidal movements

(crawl, back-crawl and butterfly)

(Maglischo, 1982)


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V t


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Vortex:mass of

wateranimated

of anorganized

rotationalmovement

Vortex (flow) visualization:


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Water aeration

Water coloration


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E i


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Extremity

vortices and

propulsive lift

theory


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Extremity vortices


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aerofoil effect

Extremity vortices

Ri ( li d )


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Ring (or cylinder)

vortices and

unsteady flowpropulsive theory

Unsteady flow


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Colwin approach


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Colwin approach

Colwin approach


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Colwin approach

Ungerecht approach


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Ungerecht approach


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Arellano

Synthesis of todayconception of human


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conception of human

swimming propulsion

We are convinced that:


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Newtonian action / reaction is present

Bernoullian lift and / or other lift forces are present

Propulsive drag force plays a very important role

Unstable flow situations are determinant

Rotating water plays a determinant role


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Thank you very much!

[email protected]

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Hydrod-Prop.pdf