Civil Engineering PE Hydraulics and Open-Channel Flow 4

Question 1

A circular culvert D = 900 mm flows full with L = 30 m, n = 0.013, and S = 0.005. Normal discharge using Manning's equation is most nearly:

Accepted Answer

2.4 m³/s

Answer

1.8 m³/s

Answer

3.0 m³/s

Answer

3.6 m³/s

Question 2

The momentum function (M) in open channel flow is most useful for analyzing:

Accepted Answer

Hydraulic jumps and rapidly varied flow

Answer

Gradually varied flow profiles

Answer

Normal depth in prismatic channels

Answer

Flow measurement over sharp-crested weirs

Question 3

In the direct step method for GVF profile computation, the channel reach length Δx between two depth sections is computed as:

Accepted Answer

Δx = ΔE / (S₀ − S̄f)

Answer

Δx = ΔE × (S₀ + S̄f)

Answer

Δx = Δy / (S₀ − S̄f)

Answer

Δx = ΔV / (S₀ − S̄f)

Question 4

A 90° V-notch (triangular) weir with Cd = 0.60 measures a head H = 0.4 m. The discharge is most nearly:

Accepted Answer

0.071 m³/s

Answer

0.056 m³/s

Answer

0.090 m³/s

Answer

0.113 m³/s

Question 5

Normal depth in an open channel is the depth at which:

Accepted Answer

The gravitational driving force equals the friction resistance (uniform flow)

Answer

The Froude number equals 1.0

Answer

Specific energy is minimized

Answer

The channel slope changes from mild to steep

Question 6

A broad-crested weir has crest elevation 100 m, upstream water surface at 101.8 m, width L = 5 m, and Cd = 0.848. Discharge is most nearly:

Accepted Answer

14.6 m³/s

Answer

10.4 m³/s

Answer

20.8 m³/s

Answer

29.2 m³/s

Question 7

When a subcritical flow channel width narrows sufficiently, 'choking' occurs at the constriction. This means:

Accepted Answer

Critical depth is forced at the throat, limiting the discharge

Answer

Flow velocity drops to zero at the throat

Answer

A hydraulic jump forms immediately upstream

Answer

The flow becomes supercritical throughout the channel