Froude number at critical flow In open-channel hydraulics, what is the value of the Froude number at critical depth/critical flow conditions?

Introduction / Context:
The Froude number Fr compares inertial forces to gravitational wave effects in open-channel flow. Identifying whether flow is subcritical, critical, or supercritical is crucial for control structures, hydraulic jumps, and energy dissipation design.

Given Data / Assumptions:

• Definition: Fr = V / sqrt(g * D), where D is hydraulic depth (A/T) or depth y for wide channels.
• Steady, prismatic channel conditions.

Concept / Approach:

Critical flow is the transition point between subcritical (Fr < 1, gravity-dominated) and supercritical (Fr > 1, inertia-dominated). At the transition, Fr equals unity; disturbances neither propagate upstream nor downstream preferentially.

Step-by-Step Solution:

Verification / Alternative check:

Empirical observations of standing waves and control sections align with the condition Fr = 1 at critical depth.

Why Other Options Are Wrong:

Values other than 1 indicate subcritical or supercritical flow regimes, not the transition point.

Common Pitfalls:

Using depth y instead of hydraulic depth D for non-wide channels; misclassifying flow regime when estimating V or D.

Final Answer:

1.0