Hi, i'm making gas-liquid flow simulations. I began with time step equal to 1e-06 s, otherwise convergence is impossible. it began then to converge, and i can fix time =1e-04s, but after a few time step, convergence is more and more difficult to reach and I have to lower the time step size. Can somebody explain me why ?????

Thanx

Try increasing the time step by smaller increments!

yes I did that, but when I get from 1e-06 to 1e-05, it takes 10 to 5 iteration per time step to converge. So I get to 1e-04, then it convergences. And after a few time steps, convergence stops. And time step size wants to be lowered. Thanx though !!!

try smaller underrelaxation parameters.

newbie

Hi you can use adaptive time stepping method in place of fixed.