2022-07 - Energy Dissipator - Tumbling Flow in Circular Culvert

Dissipation of hydraulic energy in super-critical flow circular culvert by provision of 5 rows of roughness elements (Internal / Integrated Dissipators) is simulated by Flow 3D. The animation on the top is rendered by ray tracing, while the one at the bottom is the 2D section along centreline of culvert.
This case is extracted from a worked example from Federal Highway Administration Publication No. FHWA-NHI-06-086, page 7-12. This example designs a circular culvert to use 5 rows of roughness elements to create tumbling flow to dissipate energy.
Here are the design parameters in the worked example:
Q = 2.8cms
Dia of circular culvert = 1.2m
Manning's n = 0.013
Slope = 0.06
Inflow normal flow depth and velocity = 0.445m and 7.3m/s
Target outlet velocity = less than 3m/s
This example claimed to achieve outlet velocity = 2.9m/s with 60% reduction in flow velocity. When flow passes through roughness elements, flow velocity is roughly 3m/s. Flow velocity appears to increase to about 5m/s once it leaves the last roughness element.
This type of internal dissipator can be useful if the culvert is inlet control and insufficient space to build energy dissipator beyond discharge point of culvert.

[@banditb9]

How do You implement Manning's value into OpenFoam?