Water flows uniformly 1.9 m deep in a rectangular unfinished concrete channel 4.5 m wide (Manning n = 0.014). The bed slope is S = 0.004. Use Manning’s equation in SI units to find the mean velocity V.
Open-channel flow (Manning) worksheet with answers
Water flows uniformly 0.5 m deep in a rectangular clean earth channel 6 m wide (Manning n = 0.022). The bed drops 4 m per kilometre. Use Manning’s equation in SI units to find the mean velocity V.
A concrete storm sewer with an inside diameter of 300 mm flows half full. Manning n = 0.013 and the slope is S = 0.003. Find the flow rate Q in m³/s.
A trapezoidal clean earth channel has a bottom width of 5 m and side slopes of 3:1 (horizontal:vertical). Water flows uniformly 1.6 m deep. Manning n = 0.022 and the bed slope is S = 0.003. Find the flow rate Q in m³/s.
A concrete sewer with an inside diameter of 600 mm (Manning n = 0.013) must reach a self-cleansing velocity of 0.75 m/s when flowing just full. Find the minimum slope S (in m/m).
A concrete sewer with an inside diameter of 300 mm (Manning n = 0.013) must reach a self-cleansing velocity of 1.2 m/s when flowing just full. Find the minimum slope S (in m/m).
Answer key
- 1. V = 4.608 m/s
- 2. V = 1.634 m/s
- 3. Q = 0.02648 m³/s
- 4. Q = 40 m³/s
- 5. S = 0.001193 m/m
- 6. S = 0.007694 m/m
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