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Unformatted text preview: coefficient: v v Cd  Q/(by1) For a roundnosed broadcrested weir, Eq. (10.57) applies. For an unfinished cement surface,
read
2.4 mm from Table 10.1. Then the displacement thickness is
*
L  Ans. (a) eText Main Menu  0.544 1 0.00994
0.6 m/1.2 m Textbook Table of Contents  3/2 0.528 Study Guide 0.00994 692 Chapter 10 OpenChannel Flow
The estimated flow rate is thus
Q Cdb gH3/2 0.528(4 m) (9.81 m2/s)(0.6 m)3/2 3.07 m3/s Ans. (b) Check that H/L 0.5 0.7 as required. The approach Reynolds number is V1H/
2.9 E5, just
barely below the recommended limit in Eq. (10.57).
Since V1 0.5 m/s, V2/(2g) 0.012 m, so the error in taking total head equal to 0.6 m is
1
about 2 percent. We could correct this for upstream velocity head if desired. Other ThinPlate Weir Designs Weirs are often used for flow measurement and control of artificial channels. The two
most common shapes are a rectangle and a V notch, as shown in Table 10.2. All should
be fully ventilated and not drowned.
Table 10.2a shows a fullwi...
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 Spring '08
 Sakar

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