Hi everyone,
I am working on a simulation involving restricted canal with ship using DFBI. I am facing reversed flow in my outlet boundaries as the DFBI is released (In 1.25s). Is there any method to avoid this type of wave reflection in outlet?
software using STARCCM+
VOF, implicit unsteady, K - epsilon turbulence
Thanks in advance
Howdy Anagha R H
You may find it valuable to look up a similar question asked by Jasir Jawad on Feb.22, 2023 here on ResearchGate:
How to fix reverse flow on the pressure outlet in fluent?
There is also the question asked by Ali Rezaei on Jul 13, 2024:
Why does the static pressure at the outlet become a very negative value when the outlet flow boundary conditions are used?
The reflection is due to the change of impedance as a wave expands from a plane wave in the canal to a spherical wave in the open. (Physics class answer in 1959 - professor was pleased.). Brass musical instruments and woodwinds use this natural phenomenon to create resonance in the instrument.
A "solution" to the reverse flow is to restrict the outlet so a positive pressure reflection balances the rarefaction causing the reverse flow. See the replies to Jasir Jawad's question for his experience.
It may also work to prevent the wave due to the DFBI release by removing the same volume of canal fluid simultaneously, that is to exchange volumes so there is no excess to trigger a wave.
It is good news that your simulation is so good that it produced this condition!
Happy Trails,
Len.
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