2022-09 - Energy Dissipator - Stilling Basin with Free Hydraulic Jump

Dissipation of hydraulic energy in super-critical inlet by free hydraulic jump is simulated by Flow 3D. The animation on the top shows flow velocity of the bulk water, while the one at bottom is rendered by ray tracing.
This case is extracted from a worked example from Federal Highway Administration Publication No. FHWA-NHI-06-086, page 8-6. This example designs a stilling basin to create free hydraulic jump to dissipate energy.
Here are the design parameters in the worked example:
Q = 11.8cms
Width of box culvert inlet = 3.0m
Height of box culvert inlet = 1.8m
Manning's n = 0.015
Slope = 0.065
Inflow normal flow depth and velocity = 0.463m and 8.5m/s
The only deviation from the worked example is to use 3m wide rectangular channel instead of trapezoidal channel.
The main disadvantage of energy dissipation by free hydraulic jump is the long length of stilling basin. In this worked example, total length of stilling basin is 33.7m including the sloping downward transition entering the basin, flat bottom section of basin and sloping upward transition leaving the basin.
Shorter stilling basin can be formed for the more efficient hydraulic jump.