The Froude number (Fr) in open channel flow is defined as:
Choose the correct answer
Fr = V²/(2gD)
Fr = V/√(gD) — ratio of flow velocity to wave celerity in that channel section
Fr = ρVD/μ
Fr = gD/V²
Correct Answer
B. Fr = V/√(gD) — ratio of flow velocity to wave celerity in that channel section
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Fr = V/√(gD) where V = flow velocity, D = hydraulic depth = A/T (T = top width). For rectangular channel D = y. Fr < 1: subcritical (tranquil) flow; Fr = 1: critical; Fr > 1: supercritical (rapid) flow. Fr is ratio of inertia to gravity forces in open channel (analogous to Re for viscous/inertia). Fr governs flow regime.
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