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-   -   Restarted run and change in geometry...question (http://www.cfd-online.com/Forums/cfx/22990-restarted-run-change-geometry-question.html)

Vanessa August 25, 2006 11:20

Restarted run and change in geometry...question
 
Dear all,

I had been running a problem with a certain geometry (short elastic pipe) and the first results are really difficult to get because of very complex boundary conditions. I changed my geometry (larger pipe with same diameter) and I used the result file (.res) of a previous run with a much shorter pipe as the input condition for a restarted run with my new geometry. I didn't have any problem whatsoever but I was wondering what is CFX doing with the flow variables...it is not very clear to me. My concrete question is: if my restarted simulation is running long enough, I should get appropriate results for my new pipe...or am I wrong? In any case, the initialization of my problem is extremely complicated and I am not getting results at all with a "normal" initialization...that's why I decided to use the results of a previous run (even for a much shorter pipe) as "initial guess".

Any help on this subject would be highly appreciated.

Cheers,

Vanessa


alex August 25, 2006 16:22

Re: Restarted run and change in geometry...questio
 
hi vanes'! as far as i am concerned, you could interpolate the results of your first run on the second mesh (larger pipe with the same diameter. as a consequence u are going to obtain a good initialisation and your second run will converge quikly.

Alex

Joe August 26, 2006 09:48

Re: Restarted run and change in geometry...questio
 
If you are running a steady state problem a properly converged solution should be independant of your initial guess. So you are free to use any sort of initial condition if it will help you attain convergence. However you must make sure your solution converges properly.

Robin August 28, 2006 07:55

Re: Restarted run and change in geometry...questio
 
"If you are running a steady state problem a properly converged solution should be independant of your initial guess."

This is not strictly correct. Although it is not entirely common, it is possible to create a model which has multiple stable states. The initial guess will determine which state the solution ends up in.

-Robin


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