Fluid Mechanics Questions and Answers – Most Economic Circular Section – 3

This set of Tough Fluid Mechanics Questions and Answers focuses on “Most Economic Circular Section – 3”.

1. Which of the following conditions is taken into account in case of most economical circular channel section?
a) Minimum wetted perimeter
b) Minimum wetted area
c) Maximum velocity
d) Maximum depth
View Answer

Answer: c
Explanation: In case of a circular channel the depth continuously varies, hence the wetted area and wetted perimeter changes. Therefore the condition of maximum velocity is taken under consideration.

2. What is the condition for maximum velocity in case of most economical circular section?
a) sin⁡ 2θ=2θ
b) cos⁡ 2θ=2θ
c) tan⁡ 2θ=2θ
d) sec⁡ 2θ=2θ
View Answer

Answer: c
Explanation:
The condition for maximum velocity in case of economical circular section is tan⁡ 2θ=2θ

3. What is the value of the θ in case of most economical circular channel section?
a) 128°45′
b) 129°45′
c) 130°45′
d) 131°45′
View Answer

Answer: a
Explanation: tan⁡ 2θ=2θ where θ= 128°45.
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4. What is the depth of flow in case most economical circular section considering maximum velocity?
a) 0.61D
b) 0.71D
c) 0.81D
d) 0.91D
View Answer

Answer: c
Explanation:
Depth of flow in most economical circular section considering maximum velocity is 0.81D

5. Determine the depth of flow in case of maximum velocity when the radius of the channel is 2.2m.
a) 3.56m
b) 4.56m
c) 5.56m
d) 6.56m
View Answer

Answer: a
Explanation: Depth = 0.81D = 0.81(4.4) = 3.56m.

6. The maximum discharge through a most economical circular section in case of maximum velocity is 0.16 m3/s calculate the bed slope of the channel if the radius is 0.4m and C = 55.
a) 1 in 1000
b) 1 in 1100
c) 1 in 1200
d) 1 in 1300
View Answer

Answer: c
Explanation: The bed slope of the channel if the radius is 0.4m & C = 55 is 1 in 1200

7. The maximum discharge through a circular channel is 0.38 m3/s and the radius of the channel is 0.6m. Calculate the value of C if S0=1 in 1000.
a) 45
b) 50
c) 55
d) 60
View Answer

Answer: b
Explanation: The value of C if S0=1 in 1000 is 50 if radius of the channel is 0.6m
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8. The maximum discharge through a circular channel is 0.61 m3/s and the radius of the section is 0.7m. Calculate the value of n if the bed slope value is 1 in 1100.
a) 0.018
b) 0.019
c) 0.020
d) 0.021
View Answer

Answer: c
Explanation: The value of n if the bed slope value is 1 in 1100 is 0.020

9. Calculate the hydraulic mean depth in case of maximum mean velocity if the radius of the channel is 0.5m.
a) 0.3m
b) 0.4m
c) 0.5m
d) 0.6m
View Answer

Answer: a
Explanation: R = 0.3D = 0.3(1) = 0.3m.
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10. Calculate the depth in case of circular channel discharging to the maximum extent if the radius of the channel is 2m.
a) 1.8m
b) 2.8m
c) 3.8m
d) 4.8m
View Answer

Answer: c
Explanation: Depth = 0.95D = 0.95(4) = 3.8m.

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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