Unformatted text preview: A 2y2 3.21 m2 A
y b 2.53 m Ans. It is constructive to see what flow rate a halfhexagon and semicircle would carry for the same
area of 3.214 m2.
For the halfhexagon (HH), with
1/31/2 0.577, Eq. (10.25) predicts
2
yHH[2(1 A
or yHH 1.362 m, whence Rh
Q 0.5772)1/2
1
2 y 0.577] 2
1.732yHH 3.214 0.681 m. The halfhexagon flow rate is thus 1.0
(3.214)(0.681)2/3(0.001)1/2
0.015 5.25 m3/s or about 5 percent more than that for the rectangle.
D2/8, or D 2.861 m, whence P
For a semicircle, A 3.214 m2
Rh A/P 3.214/4.484 0.715 m. The semicircle flow rate will thus be
Q 1.0
(3.214)(0.715)2/3(0.001)1/2
0.015 1
2 D 4.494 m and 5.42 m3/s or about 8 percent more than that of the rectangle and 3 percent more than that of the halfhexagon. 10.4 Specific Energy;
Critical Depth As suggested by Bakhmeteff [13] in 1911, the specific energy E is a useful parameter
in channel flow  v v E  eText Main Menu  y Textbook Table of Contents V2
2g  (10.28) Study Guide 672 Chapter 10 OpenChannel Flow where y is the water depth. It is seen from Fig. 10.8a that E is the height...
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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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