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Qmax 0.718
2.129 n
n 1/2
R2/3S0 at 128.73° and y (10.20)
in Fig. 10.6b. 0.813D
(10.21) 1/2
R8/3S0 at 151.21° and y 0.938D As shown in Fig. 10.6b, the maximum velocity is 14 percent more than the velocity
when running full, and similarly the maximum discharge is 8 percent more. Since real
pipes running nearly full tend to have somewhat unstable flow, these differences are
not that significant.  v v 10.3 Efficient UniformFlow
Channels  The simplicity of Manning’s formulation (10.19) enables us to analyze channel flows
to determine the most efficient lowresistance sections for given conditions. The most
common problem is that of maximizing Rh for a given flow area and discharge. Since
Rh A/P, maximizing Rh for given A is the same as minimizing the wetted perimeter eText Main Menu  Textbook Table of Contents  Study Guide 670 Chapter 10 OpenChannel Flow
αy α = cot θ y θ W Fig. 10.7 Geometry of a trapezoidal
channel section. b P. There is no general solution for arbitrary cross sections, but an...
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 Spring '08
 Sakar

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