Aeration vents are incorporated to minimize internal saturation pressure ____________________?
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Answer: B. In a suppressed weir
Explanation
Aeration vents are installed beneath suppressed weirs to prevent a partial vacuum from forming under the nappe. A suppressed weir lacks end contractions, causing air to be trapped beneath the overflowing sheet of water. Introducing ventilation pipes balances the internal pressure and prevents dangerous oscillations of the water nappe. A suppressed weir spans the full width of the rectangular channel without any side contractions restricting flow. Falling water can drag surrounding air downward, creating a partial vacuum chamber directly beneath the nappe. Hydraulic engineers install side air vents to maintain atmospheric pressure conditions under the overflowing water sheet.
Weirs with end contractions naturally allow atmospheric air to enter from the sides, rendering separate vents unnecessary. Cippoletti weirs feature trapezoidal side slopes that inherently provide sufficient side ventilation without extra piping. Stating that all weirs need aeration vents is incorrect because contracted designs admit air freely from the sides.
- Subject
- Agriculture
- Category
- Agriculture
- Topic
- —
- Difficulty
- medium
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