[moon1808]

Hello everyone.

I am a student learning CFD using ANSYS Fluent 18. For a project, I am doing the CFD analysis of the GA(W)-2 supercritical airfoil. I have opted for Spalart Allmaras viscosity model,taken my fluid (air) as an ideal gas with a constant value of viscosity and taken 'pressure far-field' boundary conditions. I have taken my Mach number between 0.2-0.25, and taken gauge pressure as 0.
In order to get a converged solution, I have chosen the Coupled solver and activated Pseudo-transient analysis. I have done standard initialization of the cases and have set the number of iterations to 2000.
Once the solution calculation is started for higher AOA, the continuity solution residuals decrease till ~1500 iterations and the cl value increases to the required experimental level . Then all of a sudden the continuity residual rapidly increases and within 100 iterations the cl value drops rapidly beyond which it has more or less the same low value. I increased the number of iterations upto even 10000, and have observed that the continuity residuals oscillate with a very large amplitude (0.07- 1.4). This problem does not occur at lower angles of attack (below 8 degree AOA).
I am unable to upload the case right now as it is on another computer, but if anyone has understood it, request you to help me with this problem