Ivar KJELBERG
COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted:
1 decade ago
2012年7月16日 GMT-4 14:23
Hi
check carefull if you have the results of the stationay study that are couple as initial solution for the time series study (dependent variable solver sub-node). If this is OK, then you must have a BC missing or something that makes your time series solution unique, or perhaps the time stepping settings (if you have a periodic BC condition, use a time stepping of strict or intermediat and NOT automatic type
--
Good luck
Ivar
Hi
check carefull if you have the results of the stationay study that are couple as initial solution for the time series study (dependent variable solver sub-node). If this is OK, then you must have a BC missing or something that makes your time series solution unique, or perhaps the time stepping settings (if you have a periodic BC condition, use a time stepping of strict or intermediat and NOT automatic type
--
Good luck
Ivar
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Posted:
1 decade ago
2012年7月18日 GMT-4 06:20
hey
i am trying to simulate a laminar 3d pipeflow.
my pipe is oriented in vertical direction and fluid is flowing from up to down with an inlet normal velocity of 10^-5.
i have used gravity as volume force and applied in downward vertical direction and the outlet pressure i have specified is 0( i dont know whether it should be zero or something else.).
i have used LU preconditioner but it's showing the same error i.e., "Divergence of the linear iterations.
Returned solution is not converged."
please help me out.
regards
hey
i am trying to simulate a laminar 3d pipeflow.
my pipe is oriented in vertical direction and fluid is flowing from up to down with an inlet normal velocity of 10^-5.
i have used gravity as volume force and applied in downward vertical direction and the outlet pressure i have specified is 0( i dont know whether it should be zero or something else.).
i have used LU preconditioner but it's showing the same error i.e., "Divergence of the linear iterations.
Returned solution is not converged."
please help me out.
regards
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Posted:
1 decade ago
2012年7月20日 GMT-4 02:43
Hi,
I believe you should have an inlet boundary condition and a corresponding "Outlet-Zero pressure, no viscous stress" boundary condition. All other boundary condition should be no-slip. Most of the times, I get this error when it's a meshing issue, so try making the mesh really really fine. Also, try BICGSTAB solver.
Hope this helps!
-Nitesh
Hi,
I believe you should have an inlet boundary condition and a corresponding "Outlet-Zero pressure, no viscous stress" boundary condition. All other boundary condition should be no-slip. Most of the times, I get this error when it's a meshing issue, so try making the mesh really really fine. Also, try BICGSTAB solver.
Hope this helps!
-Nitesh
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Posted:
1 decade ago
2012年7月20日 GMT-4 03:24
Hi,
To put it simply, Comsol has stopped working with incomplete LU iterative solver (don't ask me why) in CFD, you may switch to a direct method if you have enough RAM or to a multigrid iterative solver.
It would be interesting to know whether incomplete LU stopped working also for other packages, does anyone know?
Cheers
Hi,
To put it simply, Comsol has stopped working with incomplete LU iterative solver (don't ask me why) in CFD, you may switch to a direct method if you have enough RAM or to a multigrid iterative solver.
It would be interesting to know whether incomplete LU stopped working also for other packages, does anyone know?
Cheers