Negative Lift Coefficient

    • siddo23

      Hi all, I am simulating a compressible external flow using Spalart Allmaras model to determine lift and drag for an aircraft structure with external stores. I am using pressure far field.

      I realised my mesh is not too fine but I have limitations in the sense that my domain is large (boundary of 300m, 20x object size) so very fine mesh takes some time for me. For this kind of flow, what kind of y+ values am I supposed to be getting as I am getting very large numbers, and how do I resolve that.

      Also, I am obtaining negative lift coefficient in the simulation. I will attach some screenshots of my parameters, mesh and results. Could someone assist me with this?

      I am not a CFD expert so apologies on errors made. Any small amounts of help would be greatly appreciated!

    • Rob
      Ansys Employee
      I'm not sure from the images how you've linked the aircraft mesh with the main body as I'd expect to see a conformal mesh at that point. You also don't need to mesh inside the aircraft if you're just interested in the external flow. nHave a look at the NACA airfoil tutorials & videos in Help, they'll guide your settings. They will also explain how the lift & drag coefficients work. nFor an accurate solution y+ on the aircraft wants to be about 1, you achieve this with a finer mesh. n
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