Fluids

Fluids

about moving reference frame

    • ucla278924569
      Subscriber

      in my simulation, a Couette flow (water, vwall=0.1m/s) pass over a cavity filled with air.

      A transient result is got and seems to be steady. Also, a moving reference Vf=-1m/s is applied for suppressing parasitic current due to the CSF model.

    • Karthik R
      Administrator
      Hello,nCould you please highlight which walls these last two boundary conditions correspond to?nAlso, is your entire computational domain acting as MRF? nThanks.nKarthikn
    • ucla278924569
      Subscriber
      Hi Karthik,nnhere are the boundaries. Let me know if any is not clear.nnBestnJianhuann
    • ucla278924569
      Subscriber
      forget to mention the cavity has a depth of 1e-4m. Thus, in the velocity profile, the part from y=0 to y=5e-4 is the channel and the part below it is the cavity.n
    • ucla278924569
      Subscriber
      Hi Karthik,nnQ:is your entire computational domain acting as MRF?nA: I think so. I have no separate domain there. There is only one cell zone and the reference frame is applied to it.n
    • Karthik R
      Administrator
      Why are you specifying a velocity of 1 m/s at all the walls with respect to the absolute frame of reference? n
    • ucla278924569
      Subscriber
      No. I don't think I did so. The walls are absolutely 0 m/s. The upper one is absolutely 0.1m/s.n
    • Karthik R
      Administrator
      Hello,nPlease have a look at this HW problem in the Laminar Boundary Layer flow problem to verify your MRF set-up. Here, a moving flat plate problem is modeling using MRF. I understand that there is no multiphase, but this set-up should help you identify if there is anything missing in your model. Please verify this and let me know that your boundary conditions (especially all the walls) are being set properly. nAlso, if you find this resource useful, please enroll into these free Ansys Innovation Courses to learn about other Fluids topics. We are constantly adding more such courses for Fluids, Structures, and Electronics.nThank you.nKarthikn
    • ucla278924569
      Subscriber
      Hi,nI read the problem. I think my setting is correct because, in my case, the cell should be stationary relative to the absolute frame. And other setting is the same with the case without MRF. The reference frame is only on the purpose make the velocity large enough to mask the parasitic current due to VOF and CSF model. nhere is the result without moving reference frame. The big velocities (light blue x= 3e-4 and blue x=2e-4) at y=0m are consider unphysical by me. nAlthough I am not 100% sure if they are unphysical, I expect these 2 simulations will be same if they are physical. I expect they are not the same if they are unphysical while the paper is correct as well which I believe the paper is correct.n
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