Trapezoidal channel having bed width 8 m. flow depth 3 m, side slope 2H : 1.5V. Manning's rugosity coefficient 0.025 and bed slope 1 in 10000, is having velocity of:
(assume 2.0⁶⁶⁷ = 1.6)

Question

Question

This question was previously asked in

OSSC JE Civil Mains Official Paper: (Held On: 16th July 2023)

Answer 1

Concept:

As per manning's, velocity is given by,

Where,

V = Velocity, R = Hydraulic radius and S = slope

n = Mannings coefficient or rugosity factor

Discharge is given by,

Q = A × V

Where, A = area of the channel

For a trapezoidal section,

Area,

Perimeter is given by,

Hydraulic radius,

Calculation:

Given,

n = 0.025, S = 1 in 10000 or 0.0001

b = 8 m

m = 2/1.5 = 1.33 ( side slope)

d = 3 m ( flow depth)

P = 17.996 m

Now, using Manning's equation:

( Given 2.0667 = 1.6)