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FSI Problems
Posted Mar 6, 2012, 8:48 a.m. EST Mesh, Studies & Solvers Version 4.2, Version 5.2 4 Replies
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I am new to COMSOL and currently have a time dependent FSI model with numerous problems. The model is that of a fluid flow over an elastic material that should (hopefully) deform similar to the example 361 with different geometry. I used this example model for the basis of my model and am now having problem changing some of the values.
I am not able to reduce the youngs modulus of my model from 1e5 to 2e4 or even 9e4. When
doing this I recieve complaints that the non linear solver did not converge.
I also can not put in a simple equation for the velocity of u=a*t where u is the velocity
of the flow, a is an acceloration. When entering this into my model I get an error that
COMSOL could not find consistent initial values. I can get the model to run, however, if
I change the velocity equation to that given in example 361 on the website for u_in.
I have also tried automatic remeshing as I am using COMSOL 4.2, however, I coould not get
this to work either as there is NO dynamic help on this. I have also tried remeshing by
hand when the model experiences a poor mesh quality but then obtained errors about
inconsistancies in the stiffness matrix.
I will be greatful for the help
Kelly
I am not able to reduce the youngs modulus of my model from 1e5 to 2e4 or even 9e4. When
doing this I recieve complaints that the non linear solver did not converge.
I also can not put in a simple equation for the velocity of u=a*t where u is the velocity
of the flow, a is an acceloration. When entering this into my model I get an error that
COMSOL could not find consistent initial values. I can get the model to run, however, if
I change the velocity equation to that given in example 361 on the website for u_in.
I have also tried automatic remeshing as I am using COMSOL 4.2, however, I coould not get
this to work either as there is NO dynamic help on this. I have also tried remeshing by
hand when the model experiences a poor mesh quality but then obtained errors about
inconsistancies in the stiffness matrix.
I will be greatful for the help
Kelly
4 Replies Last Post Jun 20, 2016, 3:13 a.m. EDT
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Posted:
1 decade ago
Try using the Fully Coupled Solver instead of the Segregated Solver. It sometimes works better when the structure is soft. Also, for the inlet velocity consider a ramp function instead of v=a*t. If the function has zero initial velocities and accelerations the solver should be able to find consistent initial values.
Nagi Elabbasi
Veryst Engineering
Nagi Elabbasi
Veryst Engineering
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Posted:
1 decade ago
I tried using a fully coupled solver but it still wont let me put in a youngs modulus less than 1e5 it also produces a lot of inverted mesh elements
Kelly
Kelly
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Posted:
1 decade ago
Sometimes, the time-dependent problems converge better when you use the solution of the stationary problem as the initial condition to the time-dependent problem.This may help with the inverted mesh elements also.
If the stationary problem does not converge, try solving the stationary problem using a parametric solver. It usually works. Then you can use that as the initial condition for the time-dependent problem.
Sirisha
If the stationary problem does not converge, try solving the stationary problem using a parametric solver. It usually works. Then you can use that as the initial condition for the time-dependent problem.
Sirisha
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Posted:
8 years ago
Hello
I am simulating a solid body moving in fluid(air) giving the solid domain Prescribed velocity as a funtion of time. I have defined the inlet velocity as 10m/s and outlet pressure as 0 Pa.I am using automatic remeshing feature too. I wish to study the henceforth effects in fluid and the pressure variations over the solid body.
But i get the error: Condition for remeshing fulfilled for initial time.
Please help me through.
Thank You
Ankush
I am simulating a solid body moving in fluid(air) giving the solid domain Prescribed velocity as a funtion of time. I have defined the inlet velocity as 10m/s and outlet pressure as 0 Pa.I am using automatic remeshing feature too. I wish to study the henceforth effects in fluid and the pressure variations over the solid body.
But i get the error: Condition for remeshing fulfilled for initial time.
Please help me through.
Thank You
Ankush