Water Resources and Environmental Engineering

Hydraulic Jump

An abrupt rise in water surface where supercritical flow turns subcritical, dissipating energy.

A hydraulic jump forms where fast, shallow supercritical flow meets deeper subcritical flow — below a spillway or a sluice gate, for example. Momentum is conserved across it but energy is not: the turbulent roller converts a large share of the flow’s energy to heat.

In a rectangular channel the depth after the jump is y₂ = (y₁/2)[−1 + √(1 + 8Fr₁²)], and the energy lost is (y₂ − y₁)³/(4y₁y₂). Stilling basins are designed to hold the jump in place so that the dissipation happens on a concrete apron rather than in the erodible channel downstream.

How much of the FE Civil exam is Water Resources and Environmental Engineering?