High drop in residuals

star · February 16, 2014, 06:03

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..

Anna Tian · February 16, 2014, 06:39

Quote:

Originally Posted by star

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.

star · February 16, 2014, 07:51

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

February 16, 2014, 06:03	High drop in residuals	#1
star Member Harry Join Date: May 2013 Posts: 68 Rep Power: 13	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..

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February 16, 2014, 07:51		#3
star Member Harry Join Date: May 2013 Posts: 68 Rep Power: 13	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