Question

Which of the following is true?

(a) HGL always drops in the direction of flow

(b) HGL always rises in the direction of flow

(c) HGL always remains constant in the direction of flow

(d) HGL may or may not in the direction of flow

The question was posed to me in an international level competition.

The query is from Hydraulic Gradient and Total Energy Line topic in portion Flow Through Pipes of Fluid Mechanics

Answer 1

Correct choice is (d) HGL may or may not in the direction of flow

The best explanation: HGL is obtained by plotting piezometric head at various points along the axis of the pipe. Since pressure may either rise or fall in the direction of flow, HGL may or may not change in that direction.