Question

Which head loss formula is also applicable to turbulent flow in pressure conduits?

(a) Darch-Weisbach equation

(b) Manning’s formula

(c) Hazen-Williams formula

(d) Both Darch-Weisbach and Manning’s formula

I have been asked this question at a job interview.

My enquiry is from Pressure Conduites topic in section Pressure Conduits, Outlet Works through Dams and Rivers of Irrigation Engineering

Answer 1

Correct option is (b) Manning’s formula

Easiest explanation: Manning’s formula is also applicable to the turbulent flow in pressure conduits. It yields good results provided the roughness coefficient is accurately determined. The head loss is expressed as –

HL = n^2. V^2. L / R^4/3 where, n = manning’s rugosity coefficient, L is the length of pipe, V is the flow velocity through pipe and R is the hydraulic mean depth of the pipe.