2021-08 - Super-critical flow diversion

Diversion of flow in super-critical flow regime is simulated by OpenFOAM. This simulation illustrates the importance of guide wall for effective diversion of super-critical flow. It is inspired by a similar local drainage improvement problem.

Numerical experiments are set-up under the following conditions:
- Channel width = 5m
- Inflow depth = 1m
- Inflow velocity = 5m/s (Fr = 1.6)
- Width of diversion channel = 1.5m @ 45-deg

For numerical experiment on the left, fast moving super-critical flow bypasses opening of diversion channel. Only about 9% of flow is diverted in this case.

With guide wall added, three times more flow (28%) is being diverted. Width of diversion channel is about 30% of the main channel width, and similar proportion of flow is diverted.

Diversion and junction of super-critical flow is interesting as the flow behavior is different from that of commonly observed sub-critical flow. Super-critical flow junction can be found in my previous simulation below: