GATE Civil Engineering (CE) 2019 Shift 1 Solved Paper

Question : 56 of 65

Marks: +1, -0

A rectangular open channel has a width of

5 {m}

and a bed slope of

0.001

. For a uniform flow of depth

2 {m}

, the velocity is

2 {m} \/ {s}

. The Manning's roughness coefficient for the channel is

Solution:

For a rectangular channel
Width of channel

=5 {m}

Depth of flow

=2 {m}

Bed slope

=0.001

Velocity

{V}=2 {m} {/} {sec}

From manning's

V=\;{1}/{n} R^{2 {/} 2} S^{1 \/ z}

Where

R=\;{A}/{P}=\;{5 × 2}/{5+2 × 2}=1.111 {m}

⇒ 2=\;{1}/{n} ×(1.111)^{2 {/} 3} ×(0.001)^{1 {/} 2}

⇒n=0.017

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