- **OpenFOAM Running, Solving & CFD**
(*https://www.cfd-online.com/Forums/openfoam-solving/*)

- - **Strange values for Lift & Drag Coefficient**
(*https://www.cfd-online.com/Forums/openfoam-solving/94547-strange-values-lift-drag-coefficient.html*)

Strange values for Lift & Drag CoefficientHi,
i'm trying to simulate the flow over a symmetric airfoil and computing the lift and drag coefficients. The Reynolds Number is 1e6 and i'm using the Spalart Allmaras turbulance modell. The angle of attack is 0 Here is the function to compute the coefficients: Code:
`functions` Code:
`SIMPLE solution converged in 319 iterations` Denis |

Denis,
Your Aref and LRef are likely the reason you are getting such huge lift and drag coefficients. It is not unusual for a very small lift coefficient at 0 degrees (your lift is 65 times smaller than the drag) due to not quite perfect symmetry of the mesh surface. It is pretty difficult to get it exactly 0 with most meshers. Regards, Dave |

1 Attachment(s)
Hi Dave,
thank you for your reply! Ok I understand that the lift-coefficient has not to be exactly zero. The main problem is the extreme high value. I attached a picture of the model. It looks like a NACA airfoil, but it is actually a fin. So I expected a lift coefficients between 0 and 4. So do you think that this is a "phyiscal" solution? Denis |

Denis,
As I said in my prior post, I think the issue is your Aref. You could manually calculate the coefficients from your force output: "type forces" rather than "type forcecoeff" to confirm that your simulation is producing physically the right results. Dave |

All times are GMT -4. The time now is 12:25. |