Civil Engineering MCQAE Level Civil Engineering
Lacey regime theory for stable alluvial channels defines the hydraulic mean radius R in terms of discharge Q and silt factor f as:
Irrigation EngineeringLacey Regime TheoryMEDIUM
Choose the correct answer
A
R = 0.47 (Q/f)^(1/3)
B
R = 0.47 sqrt(Q/f)
C
R = (Q/f)^(2/3) / 0.47
D
R = Q / (0.47 f)
Correct Answer
A. R = 0.47 (Q/f)^(1/3)
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Lacey regime equations: V = 0.6395 sqrt(fR) (velocity), P = 4.75 sqrt(Q) (wetted perimeter), R = 0.47 (Q/f)^(1/3) (hydraulic radius), S = f^(5/3) / (3340 Q^(1/6)) (bed slope). Silt factor f = 1.76 sqrt(m_r) where m_r = median particle size (mm).
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