Transcript Fluid Flow - University of Iowa

Fluid Flow
Hydrodynamics
Aerodynamics
• Bernoulli’s Principle
• Poiseuille’s Law
Wind tunnel visualization of air flow
streamlines
AIR
FLOW
Streamlines and fluid flow
• The black lines are the
paths that the fluid takes
as it flows.
• Wider spacing indicates
low speed flow, narrow
spacing indicates high
speed flow
• Color indicates pressure
High
pressure
Low
pressure
Bernoulli’s Principle
 Fluid flow velocity = v
 Fluid pressure = P
 where v is high, P is low
 where v is low, P is high
Blowing air over the top of the tube lowers the
air pressure on that side allowing the fluid to rise
Bernoulli's Principle
P1  v  gy1  P2  v  gy2
1
2
2
1
1
2
2
2
Streamlines around a wing
From the perspective of the jet, the air is moving past it
High speed  low pressure
Low speed  high pressure
Flow over an airplane wing
11.10 Applications of Bernoulli’s Equation
11.11 Viscous Flow
POISEUILLE’S LAW
 R 4  P2  P1 
The volume flow rate is given by: QV 
8 L
 is a constant called the viscosity- it is a measure
of the resistance of the liquid to flowing (i. e., “thickness”)
POISEUILLE’S LAW
100
80
60
40
20
0
0
0.2
0.4
0.6
R/R
0
0.8
1