Calculate the corresponding hydraulic mean depth that would exist in the channel if the bed was unrippled. The rugosity coefficient in an unrippled channel is 0.015 and the rugosity coefficient actually observed by experiments on the rippled bed of channel is 0.020. Consider the value of hydraulic mean depth of the channel as 1.5 m.

Question

Calculate the corresponding hydraulic mean depth that would exist in the channel if the bed was unrippled. The rugosity coefficient in an unrippled channel is 0.015 and the rugosity coefficient actually observed by experiments on the rippled bed of channel is 0.020. Consider the value of hydraulic mean depth of the channel as 1.5 m.

asked Aug 19, 2023 in Irrigation Engineering by Carter (75.2k points)

Calculate the corresponding hydraulic mean depth that would exist in the channel if the bed was unrippled. The rugosity coefficient in an unrippled channel is 0.015 and the rugosity coefficient actually observed by experiments on the rippled bed of channel is 0.020. Consider the value of hydraulic mean depth of the channel as 1.5 m.

(a) 1.5 m

(b) 2.5 m

(c) 0.97 m

(d) 0.77 m

The question was posed to me by my school teacher while I was bunking the class.

This is a very interesting question from Sediment Transport topic in section Sediment Transport and Irrigation Channels Design of Irrigation Engineering

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Greg · Answer 1 · 2023-08-22T15:30:42+0000

Correct choice is (c) 0.97 m

The best I can explain: The formula that is used to take into account the effect of bed ripples is-

R’ = R (n’/n) ^3/2 where, R = 1.5 m, n’ = 0.015, and n = 0.020

R’ = 1.5 x (0.015/0.020)^3/2 = 0.97 m.

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