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time dependent chds simulation doesn't converge
Posted Jan 24, 2012, 4:00 p.m. EST Microfluidics, Geometry, Studies & Solvers Version 4.2a 1 Reply
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hey all,
I've done a very simple geometry swap for the electroosmostic micro-mixer example. I deleted the original geometry from the model that comsol distributes and put in my own simple 2D geometry. I then reassigned all the boundary conditions, and hit run.
It didn't .
It crashes saying that the last time step didn't converge in the time-dependent solver. I tried changing the solver (MUMPS, SPOOLES,...), but that didn't help either. Everything is as it was originally, except for geometry specific reassignments. What am I doing wrong?
thanks
Mikiyas
I've done a very simple geometry swap for the electroosmostic micro-mixer example. I deleted the original geometry from the model that comsol distributes and put in my own simple 2D geometry. I then reassigned all the boundary conditions, and hit run.
It didn't .
It crashes saying that the last time step didn't converge in the time-dependent solver. I tried changing the solver (MUMPS, SPOOLES,...), but that didn't help either. Everything is as it was originally, except for geometry specific reassignments. What am I doing wrong?
thanks
Mikiyas
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1 Reply Last Post Jan 25, 2012, 2:52 a.m. EST
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Posted:
1 decade ago
Hi
I believe you have still a little homework to do ;)
You are not using the default COMSOL physics boundaries and you have not used boundary layer meshes so you do not resolve the flow along the walls correctly. And have you checked your Reynolds number and Reynolds Cell number ? check the doc on mesh size related to physics and to time dependent solutions
then I suppose you want the stationary to not solve for the CHDS and leave that for the time series or ? (not the most important) when you do not solve for all physics, be sure you define correctly the values to use for the dependent variables "not solved for"
And when you mix several solvers, do not forget that the last Data set is the first Store solution and the first Data set is the final result, this is easy to get wrong (probably not your case anyhow)
Interesting model ;)
--
Good luck
Ivar
I believe you have still a little homework to do ;)
You are not using the default COMSOL physics boundaries and you have not used boundary layer meshes so you do not resolve the flow along the walls correctly. And have you checked your Reynolds number and Reynolds Cell number ? check the doc on mesh size related to physics and to time dependent solutions
then I suppose you want the stationary to not solve for the CHDS and leave that for the time series or ? (not the most important) when you do not solve for all physics, be sure you define correctly the values to use for the dependent variables "not solved for"
And when you mix several solvers, do not forget that the last Data set is the first Store solution and the first Data set is the final result, this is easy to get wrong (probably not your case anyhow)
Interesting model ;)
--
Good luck
Ivar