Question

Which of the following loss is not considered while calculating the total head loss between the inlet well and D/s FSL?

(a) Entry and exit losses

(b) Loss due to friction

(c) Loss due to enlargement of the section

(d) Loss due to contraction of section

The question was posed to me during an internship interview.

This intriguing question originated from Canal Falls in chapter Canal Falls of Irrigation Engineering

Answer 1

Right answer is (d) Loss due to contraction of section

To elaborate: The head loss between the inlet well and the D/s FSL is given by adding the losses due to entry, exit, loss due to sudden enlargement and loss due to friction in the pipe.

HL = 0.5 V2^2/2g (Entry loss) + (V^2 – V^3)^2/2g (sudden enlargement loss) + fLV3^2/2gd (Friction loss) + V3^2/2g (Exit loss)

Where, V2 = Velocity of entry in pipe, V3 = Velocity through the pipe, L = assumed pipe length, d = diameter of the pipe, f = Darcy’s coefficient of friction = 0.012 and g = acceleration due to gravity.