What phenomenon occurs when there is a sudden deceleration of water flow in a closed conduit?

What phenomenon occurs when there is a sudden deceleration of water flow in a closed conduit?

• A. Cavitation
• B. Hydraulic Shock
• C. Water Hammer
• D. Surge

Answer: (B)

The phenomenon being tested is a hydraulic shock: when moving water in a closed pipe is forced to decelerate suddenly, the fluid’s inertia keeps it pushing forward, creating a rapid pressure rise that travels as a shock through the system. In a constrained conduit, this momentum change shows up as a surge of pressure—the water hammer effect—because the energy of the moving water can’t dissipate instantaneously. While people often hear the term water hammer for this same event, the idea here is the abrupt pressure spike caused by the sudden stop of flow, which is what hydraulic shock describes. Cavitation happens when pressure drops below vapor pressure and forms vapor pockets, not when flow is abruptly slowed. Surge is a broader term for transient pressure waves in pipes and doesn’t pinpoint the immediate cause, which is the sudden deceleration of flow.

The phenomenon being tested is a hydraulic shock: when moving water in a closed pipe is forced to decelerate suddenly, the fluid’s inertia keeps it pushing forward, creating a rapid pressure rise that travels as a shock through the system. In a constrained conduit, this momentum change shows up as a surge of pressure—the water hammer effect—because the energy of the moving water can’t dissipate instantaneously. While people often hear the term water hammer for this same event, the idea here is the abrupt pressure spike caused by the sudden stop of flow, which is what hydraulic shock describes. Cavitation happens when pressure drops below vapor pressure and forms vapor pockets, not when flow is abruptly slowed. Surge is a broader term for transient pressure waves in pipes and doesn’t pinpoint the immediate cause, which is the sudden deceleration of flow.