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URGENT!!ERROR

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Hi!during the simulation an error appears:
Failed to find a solution:
In segregated group 1: The relative error (0) is greater than the relative tolerance.
Returned solution has not converged.
What means??why it appears??what can I do?
I have a tube with two obstacles fixed with a hinge. I have to analyze the interaction between fluid and the two obstacles.
Please answer me!!!!!!
Thanks!

3 Replies Last Post 9 janv. 2013, 15:46 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 8 janv. 2013, 10:46 UTC−5
Hi

sorry I cannot give you many clues, as that can come from too coarse mesh, imperfect boundary mesh, or initial conditions too far away from the final solution. FSI is tricky and require often some test and tries ...

--
Good luck
Ivar
Hi sorry I cannot give you many clues, as that can come from too coarse mesh, imperfect boundary mesh, or initial conditions too far away from the final solution. FSI is tricky and require often some test and tries ... -- Good luck Ivar

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Posted: 1 decade ago 8 janv. 2013, 10:57 UTC−5

Hi

sorry I cannot give you many clues, as that can come from too coarse mesh, imperfect boundary mesh, or initial conditions too far away from the final solution. FSI is tricky and require often some test and tries ...

--
Good luck
Ivar




These are what i've imposed:
incompressible navier stockes
subdomain settings:1=fluid domain, init=>p2(to)=100mmHg
2,3=solid domain
boundary settings:1=inlet, velocity, U=0.26m/s;
12=outlet, no viscous stress Po=0;
other=wall,no sleep
plane strain
subdomain setting:1=fluid domain
2,3=solid domain
boundary settings:4-11=fluid load
point setting:7,8=constrained
moving mesh
subdomain setting:1=fluid domain
2,3=solid domain
boundary settings:1,2,3,12=fixed
other=structural displacement
I solve with stationary segregated.
[QUOTE] Hi sorry I cannot give you many clues, as that can come from too coarse mesh, imperfect boundary mesh, or initial conditions too far away from the final solution. FSI is tricky and require often some test and tries ... -- Good luck Ivar [/QUOTE] These are what i've imposed: incompressible navier stockes subdomain settings:1=fluid domain, init=>p2(to)=100mmHg 2,3=solid domain boundary settings:1=inlet, velocity, U=0.26m/s; 12=outlet, no viscous stress Po=0; other=wall,no sleep plane strain subdomain setting:1=fluid domain 2,3=solid domain boundary settings:4-11=fluid load point setting:7,8=constrained moving mesh subdomain setting:1=fluid domain 2,3=solid domain boundary settings:1,2,3,12=fixed other=structural displacement I solve with stationary segregated.


Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 9 janv. 2013, 15:46 UTC−5
Hi
Perhaps you need to add a small initial flow velocity or a Poiseuille pressure drop ...
One way is to solve the case in stationary (sometimes, if you have enough RAM) a direct solver converges better another possible test, but not always ;) and then to use this stationary result as initial conditions for the time series one, or a parametric sweep to ram up a flow velocity ...

certainly with the progress in solvers and solver settings a more recent version would make life easier, but that might imply new purchases for you

--
Good luck
Ivar
Hi Perhaps you need to add a small initial flow velocity or a Poiseuille pressure drop ... One way is to solve the case in stationary (sometimes, if you have enough RAM) a direct solver converges better another possible test, but not always ;) and then to use this stationary result as initial conditions for the time series one, or a parametric sweep to ram up a flow velocity ... certainly with the progress in solvers and solver settings a more recent version would make life easier, but that might imply new purchases for you -- Good luck Ivar

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