ns方程.ppt

Chapter 7 Viscous Flow in Pipes
Laminar and Turbulent Flow
Laminar Flow Between Infinite Parallel Plates
Laminar Flow in a Pipe
Turbulent Flow in a Pipe
Bernoulli Equation in a Pipe
Calculation of Friction Head Loss in a Pipe
Calculation of Minor Loss in a Pipe
Calculation of Friction Head Loss in a Pipe
Solution of Pipe Flow Problems
Laminar and Turbulent Flow
1. The Reynolds Experiment 1883 Osborne Reynolds
Laminar Flow
Turbulent Flow
2. Critical Reynolds Number
The upper critical Reynolds Re = 50000
The lower critical Reynolds Re = 2000
层流
紊流
过渡区
a
b
c
d
e
lghf
lgv
lgvc
lgvc
lgvc
f
o
Re<2100 Laminar Flow
Re>4000 Turbulent Flow
3. Entrance Length and Established Flow
Entrance Length
l'
r0
d
B
A
建成层流段
起始段
层流边界层

Laminar Flow Between Infinite Parallel Plates
1. Problem : as figure shown steady
two stationary infinite parallel plates
fully-developed laminar flow
2h
1
2
2. Solution :
2h
1
2
x
y
2h
1
2
x
y
2h
1
2
x
y
The boundary conditions : no-slip condition
3. Discussion
The average velocity :
2h
1
2
x
y