Problem *4.158
[Difficulty: 3]
CS
moving
at speed U
c
d
Given:
Water jet striking moving disk
Find:
Acceleration of disk when at a height of 3 m
Solution:
Basic equations: Bernoulli; Momentum flux in z direction (treated as upwards) for linear accelerating CV
p
ρ
V
2
2
+
gz
⋅
+
constant
=
Assumptions:
1) Steady flow
2) Incompressible flow 3) Atmospheric pressure in jet 4) Uniform flow
(All in jet)
The Bernoulli equation becomes
V
0
2
2
g0
⋅
+
V
1
2
2
gz z
0
−
()
⋅
+
=
V
1
V
0
2
2g
⋅
z
0
z
−
⋅
+
=
V
1
15
m
s
⋅
⎛
⎝
⎞
⎠
2
2
9.81
×
m
s
2
⋅
03
−
⋅
m
⋅
+
=
V
1
12.9
m
s
=
The momentum equation becomes
W
−
Ma
rfz
⋅
−
w
1
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This note was uploaded on 10/19/2011 for the course EGN 3353C taught by Professor Lear during the Fall '07 term at University of Florida.
 Fall '07
 Lear
 Fluid Mechanics, Flux

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