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Unformatted text preview: al steel surfaces. From the
Moody chart, read f 0.0232. Then, from Eq. (1) above,
h (1.99 m/s)2
1
2(9.81 m/s2) For better accuracy, take Deff Dh/
has been read from Table 6.3 for b/a
ness ratio are
Reeff
From the Moody chart, read f
h 3
5 30 m
0.04 m 0.0232 3.71 m Crude ans. 0.670Dh 2.68 cm, where the correction factor 0.670
0.6. Then the corrected Reynolds number and rough VDeff 52,300 Deff 0.00172 0.0257. Then the improved computation for reservoir height is (1.99 m/s)2
1
2(9.81 m/s2) 0.0257 30 m
0.04 m 4.09 m Better ans. The uncorrected hydraulicdiameter estimate is about 9 percent low. Note that we do not replace
Dh by Deff in the ratio L/Dh in Eq. (1) since this is implicit in the definition of friction factor. Other Noncircular Cross Sections Table 6.4 Laminar Friction
Constants f Re for Rectangular and
Triangular Ducts
Rectangular
b Isosceles triangle
2 a
fReDh , deg 96.00
89.91
84.68
82.34
78.81
72.93
65.47
62.19
57.89
56.91 0
10
20
30
40
50
60
70
80
90  v v b/a
0.0
0.05
0.1
0.125
0.167
0.25
0...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.
 Spring '08
 Sakar

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