# Fluid Mechanics Questions and Answers – Gradually Varied Flow(GVF) – 4

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Gradually Varied Flow(GVF) – 4”.

1. What is the expression for head loss in case of a GVF?
a) hf = L2 Sf
b) hf = LSf
c) hf = 2LSf
d) hf = 3LSf

Explanation: Analytically loss is given by the product of length of the back water curve and slope
Therefore, hf = LSf.

2. What is the expression for the length of the backwater curve?
a) L = $$\frac{E_2-E_1}{S_f-S_0}$$
b) L = $$\frac{E_2-E_1}{S_f}$$
c) L = $$\frac{E_2-E_1}{S_0-S_f}$$
d) L = $$\frac{E_2-E_1}{S_0}$$

3. Calculate the head loss if the length of the back water curve is 25000m and Sf=0.00006.
a) 1m
b) 1.5m
c) 2.0m
d) 2.5m

Explanation: We know that hf=LSf; hf = 1.5m.

4. Estimate the slope of energy line in a GVF having length of the back water curve 30000m and head loss of 1m.
a) 1.33×10-5
b) 2.33×10-5
c) 3.33×10-5
d) 4.33×10-5

Explanation: We know that hf=LSf; Sf = 3.33×10-5.

5. Determine the length of the back water curve if E1=2.8m and E2=5.6m. Given:S0=0.00009 Sf= 0.00004.
a) 26000m
b) 36000m
c) 46000m
d) 56000m

6. If the difference between specific energies is 2m calculate the rate of change of specific energies if the length of the back water curve is 26314m.
a) 6.6×10-5m
b) 7.6×10-5m
c) 8.6×10-5m
d) 9.6×10-5m

7. Calculate the bed slope of the channel if the slope of the energy line 0.00024 and the length of the back water curve is 104166.67m. Given:E1-E2=3m.
a) 2.28×10-5
b) 3.28×10-5
c) 4.28×10-5
d) 5.28×10-5

8. If the depths in a channel are 2m and 4m and the velocities are 0.5 m/s and 0.3m/s, calculate the difference between specific energies.
a) 2m
b) 3m
c) 4m
d) 5m

9. Calculate the slope of the energy line if the bed slope of the channel is 4.81×10-5 if the depths of the channel are 2.7m and 4.7m and velocities are 1 m/s and 0.5m/s respectively.
a) 0.00002
b) 0.00003
c) 0.00004
d) 0.00005

10. The dimensions of a rectangular channel is 3m×2m and the bed slope of the channel is 1 in 1000, calculate the rate of change of depth if the rate of change of specific energy is 2×10-5m. Given: n = 0.010
a) 1.43×10-5m
b) 2.43×10-5m
c) 3.43×10-5m
d) 4.43×10-5m

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

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