22446488 Fluid Bio Mechanics Slide Show
Transcript of 22446488 Fluid Bio Mechanics Slide Show
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Fluid BiomechanicsFluid Biomechanics
The study of forces that develop
when an object moves through a
fluid medium.
Two fluids of interest
Water
Air
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Fluid forcesFluid forces
Four major fluid forces of interest:
Weight
Buoyant Force
rag
!ift
"ther Forces
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FloatationFloatation
Equilibrium:
weight of object = buoyant force
Floatation:
specific gravity < 1
weight of object < max. buoyant force
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Specific gravity:
# $ Wbody
Wwater
Center of buoyancy:
The point that is %& of volume of water
e'ual to the volume and shape of the
submerged body
CB is closer to the chest region
CG is closer to the pelvic region
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(aturalfloater
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Truefloater
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True sin)er
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Buoyant ForceBuoyant Force Archimedes Principle:
"bject in a fluid is acted on a buoyant force.
buoyant force $ weight of the fluid displaced by
the object
A body that is partially or totally immersed in
a fluid will experience an upward buoyantforce that is equal to the weight of the
volume of fluid displaced by that body
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Center of buoyancy &Center of buoyancy &
swimming performanceswimming performance
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Vwater !"#
Vboat $Vwater # $ "# $
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Vwater !"#
Vboat $Vwater "# $ "# #
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Vwater #
Vboat $Vwater "# $ # "#
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DragDragForceForce
Along the direction of motion
Opposite of relative flow
lows down the speed
!esistance
Affected by cross"section area
Affected by surface smoothness
#$ = % &$A '(
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Skin Friction / Surface DragSkin Friction / Surface Drag
Boundary layer: layer of affectedair
epends on
relative velocity
surface area
smoothness of surface
fluid *viscosity+
fabric *swim suit+, shaving body inswimming
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Profile Drag/Form DragProfile Drag/Form Drag
ue to separation of the fluid
from the boundary of the object
-ddy currents
ressure gradient
#treamlining
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Profile Drag/Form DragProfile Drag/Form Drag
depends on
cross/section
shape of the body
smoothness of the surface
bicyclist in upright v. crouched position
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Wae DragWae Drag
0esistance at the interface, due to wave
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!ift!ift
erpendicular to the direction of motion
%reated by different pressures on opposite
sides of an object due to fluid flow past theobject
Bernoulli1s principle: velocity is inversely
proportional to pressure
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Bernoullis LawBernoullis Law
Where the flow velocity is fast, the
pressure is low; where the flowvelocity is slow, the pressure is high
F! $ 2 %!A 34
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Effect of Lift in SportEffect of Lift in Sport
Variables influencing aerodynamic
lift force
Angle of rojection5 angle betweenhori)ontal and &* of projectile
!ine of Flight
Attitude Angle5 angle between hori)ontal
and long axis of projectile
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%enter of ressure
Angle of Attac) at 0elease5 angle
between projectile1s long a6is and
projection angle
Effect of Lift in SportEffect of Lift in Sport
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"he #agnus $ffect"he #agnus $ffect
The 7agnus effect
describes the curved
path that is observed
by spinning
projectiles
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"he #agnus $ffect"he #agnus $ffect
-6plained by
Bernoulli1s principleand the pressure
differences caused
by relative
differences in flow
velocities
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"op Spinning"op Spinning
3elocity of superior boundary
layer decrease
3elocity of inferior boundary
layer increase
(-T Force5 ownward
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Back SpinningBack Spinning
'elocity of superiorboundary layer
increase
'elocity of inferiorboundary layer
decrease
+,- #orce upward
!ebound
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flow
NET FORCE (up)
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Side SpinningSide Spinning
%t& spinRt side ! low pressure "one
#t side ! high pressure "one
(-T Force5 to 0t. side
't& Spin
#t side ! low pressure "oneRtside ! high pressure "one
(-T Force5 to !t. side
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