Divergence problem when airfoil exceed pitch angle

zonexo

Hi,

I've got a 2D FVM fractional step structured solver. It's used to simulate moving (oscillating, pitching) airfoil with grid deformation. Arc based TFI is used for the deforming of grids. It works well for pitch angle up to ~20deg. However, at higher angles or highly cambered airfoil, the results starts to diverge and the simulation has to be stopped. This divergence usually occur near the leading edge of the airfoil.

I've inspected the grid. It's deformed but it still seems ok (i guess). I wonder what can be done to prevent this from happening. Here's what I'm considering:

1. decrease time step 2. increase time step (avoid the high angle?) 3. increase grid no. 4. change deformation algorithm - suggestions?

I've done some initial testing but it's not too good. I wonder if there's other mtds available?

Thank you