Reading assignments
Chapter 2:
2.1, 2.2, 2.3, 2.4, 2.5.
Problem #1:
The results from the flow problem of a falling film are only valid for a laminar flow. For the
falling film, this flow regime can only obtained if the Reynolds number, defined by
4
Re
z
u
ρ
δ
µ
=
is smaller or equal 20.
1.
If the film liquid is water at 20
0
C (kinematic viscosity = 0.010037 cm
2
/s), what is the
maximum volume flow rate per unit per unit wall width W.
2.
For Re = 10, and the wall is vertical, calculate the film thickness.
3.
If one wants to choose a different coordinate system as follows: the y and z coordinates are
the same, but the x coordinate is: x = 0 at the solid wall, and
δ
at the gas liquid interface.
Show that the velocity is then given by
2
2
cos
1
2
z
g
x
u
ρ δ
β
µ
δ
δ
x
⎡
⎤
⎛
⎞
⎛
⎞
=
−
⎢
⎥
⎜
⎟
⎜
⎟
⎝
⎠
⎝
⎠
⎢
⎥
⎣
⎦
What is your comment on this choice of coordinate system?
Problem #2:
See 2.4. (Flow in the annulus) in the text book
Use the methodology for solving the viscous flow problem in the lecture notes (i.e. lecture
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 Fall '08
 Peters
 Fluid Dynamics, 10 cm, velocity distribution

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