High drop in residuals
 

Hi,
If drop in residual is high, for example, drop from 1e-01 to 1e-06 in every time step while taking about 20 inner iterations per time step for convergence. Is it OK or i should decrease time step and/or should refine my mesh etc..

That is not high. That just means your simulation is easy to converge. Grids refinement could only be due to large discretization error but nothing else. Grids independence study should be ahead of running simulation to obtain the results.

Thanks Meimei. So drop in residual either from 1e-01 to 1e-06 or 1e-03 to 1e-06 is not a big deal. Basically i want to judge quality of mesh from residual behavior. If oscillations in inner iterations for convergence is high (e.g between 20 and 40) will it effect result? if yes then where should we look at?
Thanks again