General Mechanical

General Mechanical

Acoustic Analysis with Several (>>20) Monopoles

    • CT27
      Subscriber

      Hi,


      I am working on a project involving several (thousands) of acoustic monopoles for which I am trying to find the sound propagating into an acoustic cavity inside a structure. I have been using the AWAVE command to insert acoustic monopoles into the simulation. However, Ansys only allows Wavenum to be between 1 and 20, so it seems I can only run 20 acoustic sources per simulation. Is there a way in Ansys to insert more than 20 acoustic sources in each simulation? Currently, the only option seems to be to run 20 sources at a time and superimpose the results. However, I have thousands of sources and would like to simulate at about 50 frequencies, so this would significantly increase the computation time. Any advice would be appreciated.


      I am using harmonic response with the Ansys ACT extension for Ansys 17.0.


      Thank you for your help.


      CT

    • sk_cheah
      Subscriber

      Not sure if it applies to you...


      If you have a limited number of listening nodes, you could take advantage of reciprocity by artificially putting a unit monopole at the listening location and measure the response at the thousands of 'dead' monopoles. You have to then scale the measured response at the 'dead' monopoles to calculate what you desire. 


       


      Kind regards,
      Jason

    • CT27
      Subscriber

      Jason,


      Thank you for your response. That is very helpful since I do have a limited number of listening nodes. I've performed some simulations to test the reciprocity (swapping the source and receiver locations). As expected, I got perfect reciprocity when no structure was included in the simulation. However, when I included structural coupling I did not see reciprocity in my results (Acoustic pressure at the receiver location was different when the source and receiver location was swapped). Is reciprocity only true in the case without structural coupling? I will continue to review my simulation setup to see if perhaps that is where I made a mistake.


      Thanks,


      CT

    • sk_cheah
      Subscriber

      CT,


      The strongly coupled matrix is unsymmetric. Perhaps transforming it to a symmetric formulation might help. I've not tried this myself so please let me know what you find.


      Kind regards,
      Jason

    • CT27
      Subscriber

       Jason,


      Thanks, I will investigate and test this and report back how it goes.



      CT

    • CT27
      Subscriber

      From my testing, it seems reciprocity is only an option for the case without structural coupling. Once the structure is introduced into the problem, reciprocity is not perfect for a source outside the structure and a listening node inside an internal cavity. Thank you for the advice though. This may be useful in a future project.


      It would be helpful if there is a way to insert more than 20 acoustic monopoles at a time in a simulation. It seems that the only limitation is the Wavenum. Is it arbitrary that this has to be between 1 and 20? If so, is there a workaround or an upgrade to Ansys that allows for more sources in one simulation?


      Thanks,


      CT

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