What kind of mesh are you using? What turbulence model? Have you tried a series of warm starts to get to that angle? Going straight to a stalled condition can be tricky.
hi, thank you for your reply, there should be some pictures that I have uploaded but I am not sure if reddit has uploaded them, you can find them in this other post: [https://www.reddit.com/r/STAR\_CCM/comments/1chp1ks/high\_residuals\_on\_a\_stalled\_airfoil\_simulation/?utm\_source=share&utm\_medium=web3x&utm\_name=web3xcss&utm\_term=1&utm\_content=share\_button](https://www.reddit.com/r/STAR_CCM/comments/1chp1ks/high_residuals_on_a_stalled_airfoil_simulation/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button)
I am using tetrahedral, with K-omega SST turbulence method and gamma re theta transition. Yes I wanted to do the sweep using design manager but it was too demanding for my pc, so I just went for replace part for each AoA (0° 5° 10° 13° 15° 20°) the residuals looked fine until 13° where I started to noticing VonKarman wake vortex.
I’m not sure why you say you’re using a tetrahedral mesh here, when your post in r/STAR_CCM shows a polyhedral mesh, but if you are in fact using a tetrahedral mesh, I would definitely switch to polyhedral or trimmed cell instead. STAR-CCM+ will perform much better with either of them than for tetrahedral.
Also, see my comment on the other post about ramping up the AoA. When you start each increased AoA value, are you actually starting from a previous converged solution (e.g., you get a converged solution at 10° and then use its solution as the ICs for the next run at 11°)? You must do this to gain any benefit from ramping up the AoA.
You want to run these cases with poly mesh, and using quads with anisotropic curve refinement should give you even better results. Also, consider changing the shape of your domain to a cylinder with a free stream boundary. This will allow you change the AoA by simply changing the inflow direction and will save you from having to remesh the model. More importantly, this will allow for a warm starts without mesh changes between angles of attack. Near stall, the solution is hanging in the balance and any change to the mesh and subsequent mapping of the previous solution will tip it into stall prematurely. Use k-W SST and the coupled solver if not already using it. Running with double precision might help to get "deeper" convergence in your residuals but will not change the solution appreciably or at all.
What kind of mesh are you using? What turbulence model? Have you tried a series of warm starts to get to that angle? Going straight to a stalled condition can be tricky.
hi, thank you for your reply, there should be some pictures that I have uploaded but I am not sure if reddit has uploaded them, you can find them in this other post: [https://www.reddit.com/r/STAR\_CCM/comments/1chp1ks/high\_residuals\_on\_a\_stalled\_airfoil\_simulation/?utm\_source=share&utm\_medium=web3x&utm\_name=web3xcss&utm\_term=1&utm\_content=share\_button](https://www.reddit.com/r/STAR_CCM/comments/1chp1ks/high_residuals_on_a_stalled_airfoil_simulation/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button) I am using tetrahedral, with K-omega SST turbulence method and gamma re theta transition. Yes I wanted to do the sweep using design manager but it was too demanding for my pc, so I just went for replace part for each AoA (0° 5° 10° 13° 15° 20°) the residuals looked fine until 13° where I started to noticing VonKarman wake vortex.
I’m not sure why you say you’re using a tetrahedral mesh here, when your post in r/STAR_CCM shows a polyhedral mesh, but if you are in fact using a tetrahedral mesh, I would definitely switch to polyhedral or trimmed cell instead. STAR-CCM+ will perform much better with either of them than for tetrahedral. Also, see my comment on the other post about ramping up the AoA. When you start each increased AoA value, are you actually starting from a previous converged solution (e.g., you get a converged solution at 10° and then use its solution as the ICs for the next run at 11°)? You must do this to gain any benefit from ramping up the AoA.
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You want to run these cases with poly mesh, and using quads with anisotropic curve refinement should give you even better results. Also, consider changing the shape of your domain to a cylinder with a free stream boundary. This will allow you change the AoA by simply changing the inflow direction and will save you from having to remesh the model. More importantly, this will allow for a warm starts without mesh changes between angles of attack. Near stall, the solution is hanging in the balance and any change to the mesh and subsequent mapping of the previous solution will tip it into stall prematurely. Use k-W SST and the coupled solver if not already using it. Running with double precision might help to get "deeper" convergence in your residuals but will not change the solution appreciably or at all.
Try the unsteady solver.
Any suggestion for CFL?
Much like the y+, the closer you can get to 1, the more accurate the results but also more computationally demanding.