Civil Engineering MCQAE Level Civil Engineering
At critical flow in an open channel, specific energy is minimum for a given discharge. The critical depth y_c for a rectangular channel of width b carrying discharge Q is:
Fluid MechanicsCritical DepthMEDIUM
Choose the correct answer
A
y_c = (Q2/gb2)^(1/3)
B
y_c = Q/(b x sqrt(g))
C
y_c = (Q/b)^2 / g
D
y_c = sqrt(Q/gb)
Correct Answer
A. y_c = (Q2/gb2)^(1/3)
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At critical depth: Fr = 1, V = sqrt(g x y_c). From Q = b x y_c x V: Q = b x y_c x sqrt(g x y_c) = b x sqrt(g) x y_c^(3/2). Solving: y_c = (Q2/(g x b2))^(1/3).
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