Different moment coefficient for VAWT at different courant number.
 

Hello everyone,
I am trying to simulate VAWT in 2D on openfoam 8. I have made a very good mesh, however when running the simulation on courant number 1,my moment coefficient are going negative(i.e far from experimental data), however if i increase the courant number to 10 and make sure the solver is stable, my moment coefficients are positive and much more nearby to the experimental data.


I am not able to get my head around the problem. Any help would be highly appreciated.

If anyone wants to try the case setup please email me at (amz218310@am.iitd.ac.in), i will be happy to share the case file.