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Calculating flow induced sound incident to wall

    • Gorilla Koala


      I'm looking for a way to calculate flow-induced sound propagation incident to pipe wall. At first I thought I could use the DAVA method, but it doesn't calculate flow-induced sound (https://forum.ansys.com/forums/topic/import-cgns-file-to/). 

      I'm thining to use Fluent's wave equation model to calulate the sound source. But the model treats the face between the pipe and the fluid domain as rigid boundary condition which means all the incident sound wave is relected. I want to change it to an impedance boundary condition and calculate the sound propagation inside the pipe. 

      I think using UDF (User Difined Function) may have a potential to calculate what I want to do but I have not find any relative literature so far. Would you please let me know if you have any suggestion. 

    • Hauke Reese

      Hello Gorilla Koala, The DAVA workflow is a 1 way coupling between CFD and harmonic acoustics. At first CFD calculation compressible transient simulation is done. The static pressure which represends the hydrodynamic and acoustics fluctuation are sampled at the wall. Secondly the harmonic acoustics simulation calculate the solid vibration and the sound propatation the ambient. I think this is the most strate forward way. If you uses the wave a equation you can extract the particle velocity as source via scripting and hand it over to ANSYS. Basiclly it yields to a similar approach as the DAVA workflow does but the workflow needs some scripting to extract and export the sources and it will neglect the hydrodynamic exciatation. As you point out already in both workflows the wall is also treated as sound hard and waves are reflected. I think this a valid asumption. If the effect of the solid wall need to be taking into account correctly (reflection and also vibration) a  2 way FSI is needed. 

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