Fluids

Fluids

Incorrect pressure at the outlet (for subsonic region)

    • shuvCFD
      Subscriber

      Hello All.

      I am trying to simulate a very simple supersonic flow past a flat plate as shown in the figure below (the boundary conditions and the computational grid). Given the nature of the problem and the supersonic flow at the outlet, the outlet is modelled as "pressure outlet" i.e. zero gradient extrapolation. The inlet is taken as "pressure far field".

    • Karthik R
      Administrator
      Hello What is the outlet pressure value you are specifying? Are you estimating this beyond the shock and providing this value? Please have a look at this example to understand how this can be done.
      Karthik

    • shuvCFD
      Subscriber
      Hi Karthik!
      Thanks for the reply. The video is quite relevant and yeah we did do something similar to what is done here. Essentially in this tutorial, the outlet gauge pressure is set equal to the freestream static pressure (i.e., 10400 Pa), whereas I had earlier set it equal to 0 Pa. Setting it to freestream pressure solves the issue but I wanted to know how does one decide the exit gauge pressure for such problems?
      For instance, if I set the outlet pressure equal to 5000 Pa, the exit pressure at that region becomes equal to ~5000Pa.
      Regards Shuvayan
    • Karthik R
      Administrator
      Hello Yes, this is exactly what is happening. You gauge pressure you specify will be applied as outlet static pressure. This is why you need to carefully pick your boundary condition appropriately in such problems.
      Karthik
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