divergence with hex mesh in VOF model
 

Hi all,

I am trying to model water flows in and out a tank with VOF model. The geometry is suitable for hex mesh and in fact I can create a perfect hex mesh (see attached). The tank is 1m x 1m x 1.2m, water flows in from the top left and flows out from the bottom right of the tank. The mesh size is 2 cm, and there are about 160K cells in total.

The problem is the solutions always diverge from the very first few time step. I have tried Implicit (without Implicit Body Force), PISO for pressure-velocity coupling, PRESTO for pressure under discretization. I have tried Explicit, different time step sizes (0.005, 0.01, and 0.02s) but the still got the same results. I appreciate if you can let me know what wrong with my setups.

Thanks!