Which of the following statements is/are true? i. Control section is defined as a section in which a fixed relationship exists between the discharge and the depth of flow. ii. For subcritical flow, the control section for gradually varied flow is at the upstream.
- AOnly (i)Correct
- BOnly (ii)
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Control sections in open channel flow
Formula
NONE
Step-by-step solution
1. A control section establishes a unique relation between discharge and flow depth. 2. For subcritical flow, control is located downstream, while for supercritical flow, control is located upstream. Answer: A
Explanation
A control section establishes a unique relationship between flow depth and discharge, making statement i true. However, for subcritical flow, the control section for gradually varied flow is located downstream because downstream conditions govern the flow. Thus, statement ii is false and option A is correct.
Why the other options are wrong
D) Statement (ii) is correct regarding upstream control sections in subcritical flow.
Shortcut
Control section for subcritical flow is at the downstream end (only statement i is true).
Common mistake
Selecting option C by incorrectly assuming the control section for subcritical flow is located upstream instead of downstream.
Correct answer: A) Only (i)