Civil Engineering PE Hydraulics and Open-Channel Flow 5

Question 1

The Chezy coefficient C is related to Manning's n by which expression (SI units)?

Accepted Answer

C = R^(1/6) / n

Answer

Equating Manning's V = (1/n)R^(2/3)S^(1/2) and Chezy's V = C√(RS) gives C = R^(1/6)/n.

Question 2

Flow in a steep channel (S₀ > Sc) with depth greater than critical depth carries which GVF profile classification?

Accepted Answer

S1

Answer

An S1 profile occurs on steep slopes when y > yc; depth decreases downstream toward normal depth, with flow remaining supercritical.

Question 3

A rectangular channel 3 m wide carries Q = 15 m³/s at normal depth with n = 0.014 and S₀ = 0.001. Normal depth is most nearly:

Accepted Answer

1.75 m

Answer

Using Manning's iteratively: Q = (1/0.014)(3y)[(3y/(3+2y))^(2/3)](0.001^0.5) = 15 m³/s yields yn ≈ 1.75 m.

Question 4

For a sluice gate in a wide rectangular channel with upstream depth y₁ = 2.0 m, gate opening a = 0.3 m, and Cc = 0.62, discharge per unit width assuming negligible velocity of approach is most nearly:

Accepted Answer

1.17 m²/s

Answer

q = Cc·a·√(2g·y₁) = 0.62×0.3×√(2×9.81×2.0) = 0.186×6.264 ≈ 1.17 m²/s.

Question 5

The primary purpose of a stilling basin downstream of a spillway is to:

Accepted Answer

Dissipate kinetic energy via a controlled hydraulic jump to prevent scour

Answer

A stilling basin forces a hydraulic jump, converting high-velocity supercritical flow to subcritical and dissipating kinetic energy to protect the downstream channel.

Civil Engineering PE Practice Test

Civil Engineering PE Practice Test

Civil Engineering PE Hydraulics and Open-Channel Flow 5