Applications of Bernoullis Principle faster speed slower speed more pressureless pressure If no...
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Transcript of Applications of Bernoullis Principle faster speed slower speed more pressureless pressure If no...
Applications of Bernoulli’s Principle
faster speedslower speed
more pressure less pressure
If no change in height: P + ½ρv2 = constant
P+ ρgy + ½ ρv2 = constant
As the speed of a fluid increases, the pressure in the fluid decreases.
P α 1/v
Motion of fluid energykinetic
Pressure in fluid energypotential
KE + PE is constant
d d/4v
If incompressible fluid (density = ρ),change in pressure?
Bernoulli & FlightBernoulli & Flight• Bernoulli’s Bernoulli’s
Principle is what Principle is what allows birds and allows birds and planes to fly.planes to fly.
• The secret The secret behind flight is behind flight is ‘under the wings.’‘under the wings.’
AIRFOIL
On top: greater air speed and less air pressure
On bottom: less air speed and more air pressure
DRAGDRAGTHRUSTTHRUST
LIFTLIFT
GRAVITYGRAVITY
v1
v2
Net force on wing?
½ Aρ(v22 – v1
2)
ρair = 1.29 kg/m3
Spoiler – airfoil reversed
greater air speedless pressure
less air speedmore pressure
net force: downward
Racecar
Spoiler provides better tractionand avoids lift
Wind over a roof
v
v = 0patm
proof
Patm = Proof + ½ ρv2
slow air speed
fast air speed
Curve Ball
Golf ball dimples
Winds over a mountain
Shower Curtain
Atomizer – As air passes at top of tube, the pressure decreases and fluid is drawn upthe tube.