P871 here however we simply use one dimensionalflow

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Unformatted text preview: proof, that the flow over the crest draws down to hmin H/3, the volume flow q Q/b over the crest is approximately H q crest | v v 2 3 | e-Text Main Menu | V2 dh 2g H V2)1/2 dh 1 (2gh H/3 V2 1 2g 3/2 Textbook Table of Contents H 3 | V2 1 2g 3/2 Study Guide (10.52) 690 Chapter 10 Open-Channel Flow Normally the upstream velocity head V 2/(2g) is neglected, so this expression reduces to 1 Sharp-crested theory: 0.81( 2 )(2g)1/2H3/2 3 q (10.53) This formula is functionally correct, but the coefficient 0.81 is too high and should be replaced by an experimentally determined discharge coefficient. Analysis of Broad-Crested Weirs The broad-crested weir of Fig. 10.16b can be analyzed more accurately because it creates a short run of nearly one-dimensional critical flow, as shown. Bernoulli’s equation from upstream to the weir crest yields V2 1 2g Y 2 Vc 2g H 2 If the crest is very wide into the paper, Vc yc gyc from Eq. (10.33). Thus we can solve for V2 1 3g 2H 3 yc Y 2H 3 This result was used without proof to derive Eq. (10.53...
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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.

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