Question

For what limits of Froude number, the jump is said to be weak jump?

(a) 1.1 to 2.4

(b) 1.9 to 2.9

(c) 1.5 to 2.2

(d) 1.7 to 2.5

This question was posed to me in exam.

Query is from Hydraulic Jump topic in section Diversion Head Works, Hydraulic Jump Usefulness in Irrigation Structure of Irrigation Engineering

Answer 1

Correct answer is (d) 1.7 to 2.5

Easy explanation: According to Froude number from 1.7 to 2.5 a series of rollers develop on the surface of the jump, but at the downstream side the surface is smooth. The energy loss is low and a uniform velocity is maintained. The jump under these conditions is called a weak jump.