The 'broad-crested weir' differs from a sharp-crested weir in that:
Choose the correct answer
Same formula and Cd as sharp-crested
Wide crest causes critical flow to develop on it — Q = 1.705CdLH^(3/2), Cd ≈ 0.848, different from sharp-crested
Only used for very large discharges
Has no crest (zero length)
Correct Answer
B. Wide crest causes critical flow to develop on it — Q = 1.705CdLH^(3/2), Cd ≈ 0.848, different from sharp-crested
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Broad-crested weir: crest width B such that critical flow develops on the crest (L/H > 0.5). Discharge Q = 1.705CdL H^(3/2). Cd ≈ 0.848 (broad-crested coefficient from theory). Compared to sharp-crested (Cd=0.62): broad-crested has higher Cd but critical depth y_c = 2H/3 on crest. Used for: more robust measurement, less damage from floating debris. IS 6966 covers weir design.
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