Question

For the usual turbulent flow, calculate the critical shear stress if the mean diameter of the grain particle of bed material is 0.3 mm.

(a) 0.300 N/m^2

(b) 0.106 N/m^2

(c) 0.206 N/m^2

(d) 0.116 N/m^2

This question was posed to me by my school principal while I was bunking the class.

My doubt is from Sediment Transport in chapter Sediment Transport and Irrigation Channels Design of Irrigation Engineering

Answer 1

The correct choice is (c) 0.206 N/m^2

The explanation is: For usual turbulent flow, the value of critical shear stress is given by 0.687d where d is the arithmetic average diameter of sediment in mm.

S0 = 0.687 d

S0 = 0.687 x 0.3 = 0.206 N/m^2.