Difficulty: Easy
Correct Answer: Hydraulic jump
Explanation:
Introduction / Context:
A hydraulic jump is a classic rapidly varied open-channel flow transition used to dissipate energy downstream of spillways, sluices, and culverts. It occurs when supercritical flow (high velocity, low depth, Fr > 1) is forced to transition to subcritical flow (lower velocity, greater depth, Fr < 1), producing turbulence and a visible rise in the water surface.
Given Data / Assumptions:
Concept / Approach:
The jump conserves mass and (approximately) momentum across the roller; energy is not conserved because substantial energy is dissipated by turbulence and air entrainment. Conjugate (sequent) depths y1 and y2 are related by momentum principles; the energy loss ΔE is a function of Froude number Fr1 of the incoming stream.
Step-by-Step Solution:
Verification / Alternative check:
Observation of roller, intense turbulence, and surface boil confirms a hydraulic jump. In contrast, “water hammer” is a pressure transient in closed conduits due to rapid valve action, not an open-channel phenomenon.
Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
Hydraulic jump
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