Match the flow types to their Froude number:
| List-I | List-II |
|---|---|
| A.Subcritical | 1.Fr > 1 |
| B.Supercritical | 2.Fr = 1 |
| C.Critical | 3.Fr < 1 |
- AA-3, B-1, C-2Correct
- BA-1, B-3, C-2
- CA-2, B-1, C-3
- DA-3, B-2, C-1
Solution
Concept
The Froude number represents the ratio of inertial forces to gravitational forces and determines the state of flow in open channels.
Formula
Fr = v / √(g × D), where v = velocity, g = acceleration due to gravity, and D = hydraulic depth.
Step-by-step solution
1. Identify the definition of Subcritical flow: It occurs when the flow velocity is less than the wave celerity, resulting in Fr < 1 . 2. Identify the definition of Supercritical flow: It occurs when the flow velocity is greater than the wave celerity, resulting in Fr > 1 3. Identify the definition of Critical flow: It occurs when the flow velocity equals the wave celerity, resulting in Fr = 1
Explanation
The classification of flow in open channels is based on the Froude number (Fr). If Fr < 1, the flow is subcritical (tranquil); if Fr = 1, the flow is critical; and if Fr > 1, the flow is supercritical (shooting/rapid).
Shortcut
Remember: 'Sub' means 'below' (Fr < 1) and 'Super' means 'above' (Fr > 1).
Common mistake
Confusing Froude number with Reynolds number (used for laminar/turbulent classification) or swapping the conditions for subcritical and supercritical flow.
Correct answer: A) A-3, B-1, C-2