2022-05 - Energy Dissipator - Tumbling Flow in Box Culvert
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- Опубликовано: 7 фев 2025
- Dissipation of hydraulic energy in super-critical flow box 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 same result with more engineering way of presentation.
This case is extracted from a worked example from Federal Highway Administration Publication No. FHWA-NHI-06-086, page 7-6. This example designs a concrete box 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
Width of box culvert = 1.2m
Height of box culvert = 1.2m
Manning's n = 0.013
Slope = 0.06
Inflow normal flow depth and velocity = 0.342m and 6.8m/s
Target of design = less than 3m/s with critical outlet velocity
This example claimed to achieve outlet velocity = 2.8m/s with 58% reduction in flow velocity. It is interesting to see that local flow velocity near water surface at outlet could still be 5-6m/s. However, average flow velocity over whole depth of tumbling flow appears roughly below 3m/s.
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.