Which one of the following statements is correct for flow in open channels?

Question

Question

This question was previously asked in

UPSC ESE (Prelims) Civil Engineering 19 Feb 2023 Official Paper

When the depth of flow in a channel is greater than the critical depth, the flow is said to be supercritical flow
When the depth of flow in a channel is equal to critical depth, the flow is said to be supercritical flow
When the depth of flow in a channel is less than the critical depth, the flow is said to be subcritical flow
When the depth of flow in a channel is greater than the critical depth, the flow is said to be subcritical flow

Answer 1

Explanation:

Critical flow:

It is defined as the flow at which specific energy is minimum or the flow corresponding to critical depth is defined as critical flow.
For critical flow froude number is one.

Tranquil flow or streaming flow or sub-critical flow

When the depth of a flow in a channel is greater than critical depth (hc), the flow is said to be sub-critical flow.
Froude number is less than 1 for sub-critical flow.

Torrential flow or shooting flow or super-critical flow

When the depth of a flow in a channel is less than critical depth (hc), the flow is said to be super-critical flow.
Froude number is greater than 1 for super-critical flow.

Additional InformationThe Froude number is given by,

Where,

V = Velocity of water, D = Y = Hydraulic depth = A/T, T = Top width of the channel