For a hydraulically efficient rectangular channel, the width is _______ the depth.
- Ahalf
- Bequal to
- CtwiceCorrect
- Dthrice
Solution
Concept
Dimensions of efficient rectangular open channel
Formula
b = 2 × y
Step-by-step solution
1. A rectangular channel section is hydraulically efficient when it delivers maximum discharge for a given area. 2. The theoretical condition for maximum efficiency occurs when channel width b is equal to twice the depth d (b = 2d). Answer: C
Explanation
A channel section is considered hydraulically efficient when it delivers maximum discharge for a given cross-sectional area, which occurs when the wetted perimeter is minimized. For a rectangular channel, this ideal condition occurs when the channel width is equal to twice the water depth. Therefore, option C is correct.
Why the other options are wrong
B) Equal width and depth does not give maximum hydraulic efficiency for a rectangular channel. D) Width equal to three times depth is not the condition for maximum hydraulic efficiency.
Shortcut
Most efficient rectangular channel: Width is twice the depth (b = 2y).
Common mistake
Selecting option A (half) by confusing the width-to-depth ratio with the depth-to-width ratio for a hydraulically efficient channel.
Correct answer: C) twice