negative volume and folded mash
 

Hi, Im calculating the wing's fluid-structure interaction. Now I meet a error.My wing's length and width is 1m. When the velocity of inlet is 50m/s, I set the timesteps to 0.001s. then negative volume and folded mash appeared. If I ramp up the timesteps such as 0.01 0.1 , the solver show overflow. What can I do to fix it? Thanks to everyone.
When v=1m/s, timesteps=0.1s, it works nice.
negative sector volume, nagetive element volume, folded mesh has occurred. and the location of negative volume is in the domain of fluid, not at the wing. that's wierd. the location is far away the wing

This suggests to me you have a fundamental instability in your simulation which cannot be fixed by time step size alone.

This FAQ may help: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

CFD should converge quickly and easily with small time steps. The fact your does not suggests something is very wrong.

I would try ramping up the velocity, as I believe with that high velocity it may be causing too much deformation and thus the elements fold inward on themselves causing the negative volume error. Also perhaps making your fluid domain larger will help with mesh deformation problems.