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Need some advise for Boundary Condition and Iterative method
Posted Sep 9, 2010, 11:12 a.m. EDT 3 Replies
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Hi everyone. I have started using COMSOL for sometime. I have some questions about its boundary condition and solver.
1. My test case is 2D internal fin Fluid flow+Heat transfer+ FSI+transient , and the Direct solver (UMFPACK) is used.
When I am defining the inlet velocity of 0.001m/s, the it is converged and shows nice results.
However, if I increase the velocity inlet up to 0.1 m/s, the monitor shows that " Fail to find consistent initial condition_Last time step is not converged."
2. Next problem, I am defining the inlet velocity of 0.001m/s
,and I wanna switch the solver from Direct method to Iterative method.
This time I used the GMRES and FGMRES.
Therefore, the monitor shows that "Fail to find consistent initial condition_ Matrix_has_zero_on_diagonal and Fail to find consistent initial condition _Last time step is not converged."
Does anyone has suggestion for me? Thank you very much in advance.
Suabsakul
1. My test case is 2D internal fin Fluid flow+Heat transfer+ FSI+transient , and the Direct solver (UMFPACK) is used.
When I am defining the inlet velocity of 0.001m/s, the it is converged and shows nice results.
However, if I increase the velocity inlet up to 0.1 m/s, the monitor shows that " Fail to find consistent initial condition_Last time step is not converged."
2. Next problem, I am defining the inlet velocity of 0.001m/s
,and I wanna switch the solver from Direct method to Iterative method.
This time I used the GMRES and FGMRES.
Therefore, the monitor shows that "Fail to find consistent initial condition_ Matrix_has_zero_on_diagonal and Fail to find consistent initial condition _Last time step is not converged."
Does anyone has suggestion for me? Thank you very much in advance.
Suabsakul
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3 Replies Last Post Sep 11, 2010, 3:42 p.m. EDT
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Posted:
1 decade ago
Hi
have you tried to increase gently the velocity in a parametrical sweep, and then perhpas save the model to use it as a starting point/initial conditions for next analysis ?
and if you start with 0.1 m/s velocity, perhaps you could define initial values more realistic as the default "0"
--
Good luck
Ivar
have you tried to increase gently the velocity in a parametrical sweep, and then perhpas save the model to use it as a starting point/initial conditions for next analysis ?
and if you start with 0.1 m/s velocity, perhaps you could define initial values more realistic as the default "0"
--
Good luck
Ivar
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Posted:
1 decade ago
To Ivar . Thanks for ur sugguestion. I will try to increase the velocity slightly. Also, I am gonna change the initial condition.
Best Regards,
Suabsakul
Best Regards,
Suabsakul
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Posted:
1 decade ago
Hi
an then there is the issue of the pressure, I have notived that I get often better convergenve with an outlet rather in "pressure no viscuous stress", than just "non viscous stress", the question is then what realistic pressure to use. (all for constant velocity input "inlet")
--
Good luck
Ivar
an then there is the issue of the pressure, I have notived that I get often better convergenve with an outlet rather in "pressure no viscuous stress", than just "non viscous stress", the question is then what realistic pressure to use. (all for constant velocity input "inlet")
--
Good luck
Ivar