Question

For a diffuser, the vertical intercept between EGL and HGL

(a) increases

(b) decreases

(c) remains constant

(d) may increase or decrease

This question was addressed to me in a job interview.

Asked question is from Hydraulic Gradient and Total Energy Line in chapter Flow Through Pipes of Fluid Mechanics

Answer 1

Correct answer is (b) decreases

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a diffuser, the cross-sectional area increases in the direction of flow leading to a decrease in the velocity of flow across the pipe. Since the kinetic head decreases, the vertical intercept between EGL and HGL will decrease.