GATE CE 2015 Set 1 — Question 28
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Water Resources Engineering → Open Channel Flow → Manning Equation
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Question
A circular pipe has a diameter of 1 m, bed slope of 1 in 1000, and Manning’s roughness coefficient equal to 0.01. It may be treated as an open channel flow when it is flowing just full, i.e., the water level just touches the crest. The discharge in this condition is denoted by . Similarly, the discharge when the pipe is flowing half-full, i.e., with a flow depth of 0.5 m, is denoted by . The ratio is:
Correct answer
(C) 2
Solution
For a circular pipe, the discharge is given by Manning's equation: .
.Thus, the ratio is 2.
1.Full flow condition ():
- Area
- Wetted perimeter
- Hydraulic radius
- Area
- Wetted perimeter
- Hydraulic radius
.Thus, the ratio is 2.
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