Ansys Learning Forum › Forums › Discuss Simulation › Fluids › HOW TO EXPORT LIFT COEFFICIENT AND DRAG COEFFICIENT IN FENSAP – ICE › Reply To: HOW TO EXPORT LIFT COEFFICIENT AND DRAG COEFFICIENT IN FENSAP – ICE
July 25, 2021 at 7:22 pm
Shoaib Shah
Ansys Employee
Hi Pham
Good news is that the steps you are showing are correctly done. Just like the other residuals you need the lift and drag coefficients to converge. The 1st value would be entirely wrong.
The solution has to be sufficiently (fully) converged (i.e. NS, Energy, Average residuals etc.), usually after 300-1500 iterations (depending on the case). In fact, the aerodynamic coefficients e.g. lift and drag are an additional monitor to check for convergence. In the latter cases, you would normally see the lift and drag values remain unchanged (or the delta between the final 2 iterations is really low ~0.1%).
So in a typical simple airfoil case, lets assume, the solution converges after 300 iterations. You should export the CSV, and check the last few 10-50 iterations and see the change in values in lift and drag. If they are <0.1% , a). it confirms the solution has converged or is close to convergence. and b). You could decide to either take the last value as the final lift/drag value or average out the last few iterations where there is little or no change in the lift or drag.
Good news is that the steps you are showing are correctly done. Just like the other residuals you need the lift and drag coefficients to converge. The 1st value would be entirely wrong.
The solution has to be sufficiently (fully) converged (i.e. NS, Energy, Average residuals etc.), usually after 300-1500 iterations (depending on the case). In fact, the aerodynamic coefficients e.g. lift and drag are an additional monitor to check for convergence. In the latter cases, you would normally see the lift and drag values remain unchanged (or the delta between the final 2 iterations is really low ~0.1%).
So in a typical simple airfoil case, lets assume, the solution converges after 300 iterations. You should export the CSV, and check the last few 10-50 iterations and see the change in values in lift and drag. If they are <0.1% , a). it confirms the solution has converged or is close to convergence. and b). You could decide to either take the last value as the final lift/drag value or average out the last few iterations where there is little or no change in the lift or drag.
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