To avoid interruption of flow in a siphon due to air accumulation at the highest point, where should the small air vessel (air release/vent) be provided?

Introduction / Context:
A siphon conveys liquid over a rise by maintaining a continuous column under sub-atmospheric pressure at the summit. Air can exsolve from water or be drawn in through small leaks, collecting at the top and breaking the siphon if not vented.

Given Data / Assumptions:

• Closed conduit with a summit (highest point) above both reservoirs.
• Risk of air pocket formation at the crown due to low pressure.
• Objective: maintain continuity of the water column.

Concept / Approach:
Air pockets naturally migrate to and collect at the highest point. Providing an air vessel or automatic air-release/air-admittance device at the summit purges trapped air (or admits air for controlled shutdown), preventing vapor lock and loss of prime.

Step-by-Step Solution:
Identify the point of minimum absolute pressure: the summit.Install a small air vessel/vent at this crown location.Periodically or automatically discharge accumulated air to keep the conduit liquid-full.

Verification / Alternative check:
Field practice and siphon design guidelines consistently show air-release valves at summits; CFD and model tests confirm air entrapment zones align with the geometric high point.

Why Other Options Are Wrong:
Inlet/outlet: not the locus of trapped air accumulation.Arbitrary point: ineffective unless it coincides with the crown.

Common Pitfalls:

• Omitting air release on long siphons with multiple local high points.
• Failing to provide vacuum-break for safe shutdown, leading to column separation.

Final Answer:
At the summit (crown) of the siphon