Question

In a horizontal rectangular channel, if the Froude number of an incoming supercritical flow is 6, then the jump so formed will be
1. Undular
2. Weak
3. Steady
4. Oscillating
5. Strong

Answer 1

Correct Answer - Option 3 : Steady

Concept:

Froude number is the ratio of inertial force to the gravitation force.

\(\text{Froude }\!\!~\!\!\text{ number}=\text{ }\!\!~\!\!\text{ }\sqrt{\frac{\text{Inertia force }\!\!~\!\!\text{ }}{\text{Gravitational force }\!\!~\!\!\text{ }}}\)

Froude number has the following applications:

• Used in cases of river flows, open-channel flows, spillways, surface wave motion created by boats
• It can be used for flow classification

The hydraulic jumps in horizontal rectangular channels are classified into five categories based on Froude number F₁ of the supercritical flow as:

Range	Type
1.0 < F1 ≤ 1.7	Undular jump
1.7 < F1 ≤ 2.5	Weak jump
2.5 < F1 ≤ 4.5	Oscillating jump
4.5 < F1 ≤ 9.0	Steady jump
F1 > 9.0	Strong or choppy jump