Question

At the same mean velocity, what is the ratio of head loss per unit length for a sewer pipe flowing full to that for the same pipe flowing half full ?

A. 2.0 B. 1.7 C. 1.0 D. 0.6

Answer 1

head loss due to friction/unit length of pipe is proportional to mean velocity square V² and inversely proportional to diameter D of the pipe.

V = volumetric flow rate.. remains same

So head loss due to friction : ratio when flowing full / when flowing half full = 1