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HELP!Convergence Criterium

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Old   July 26, 2005, 04:42
Default HELP!Convergence Criterium
  #1
Teresa
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Hi! In all case I do the convergence criterium depends with the residuals, could I do my own convergence criterium? I have some variables in a udf, and I want that the convergence criterium converges if,for example, x>5, being x one of my udf variables. Instead of checking convergence with the residuals I want that if x>5 fluent stops iterating and pass to the following time-step. Is it possible?How can I do?

Thank you

Teresa
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Old   July 27, 2005, 07:02
Default Re: HELP!Convergence Criterium
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Teresa
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Hi!Nobody knows how to do this or is it impossible?This question is very important to solve my problem, so any help or idea would be great! Thank you

Teresa
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Old   July 27, 2005, 07:23
Default Re: HELP!Convergence Criterium
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CFD-novice
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From my limited experience with UDFs: What you require is kind of a program control flow command or statement that instructs FLUENT to abandon an inner loop and proceed with the next iteration of an outer loop. I once tried the exit() function call from the C programming language to completely stop program execution for some debugging purposes, but did't manage to get it to work. So my answer to your question 'is this possible?' would be: no. unfortunately.

Maybe anybody else can correct me.
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Old   July 27, 2005, 08:53
Default Re: HELP!Convergence Criterium
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rajani
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Even I would like to know if its possible to have iteration control thru user defined convergence. as seen from the earlier responses, it seems this control is not available in Fluent as of now. but i can suggest oneth..

what ever be ur own convergence control.. like x>5.... even for this condition.. u need to have converged solution for velocities, temperatures or any other parameters. so, u initially solve the problem for the default values of convergence and then include an udf which involves ur own convergence criterion and also see that it prints a variable and gives an idea whether specified convergence is reached or not. after interpreting this udf.. change the convergence values a bit like may b by the order of 0.01 and then iterate again. while doing this iteration itself u will see whether the reqd convergence is reached or not by the value which gets printed (inase u give any in udf). The moment u feel ur required value is obtained,,, u can stop the iteration.

This is only my opinion and any one can correct me if i'm wrong
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Old   July 27, 2005, 11:53
Default Re: HELP!Convergence Criterium
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Teresa
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In the first part of my project I've implemented an udf, and I've checked how many iterations/time-step I needed to converge my problem, and I did all simulations with this iteration number. My question was, if the udf could do this itself and then pass the order to stop iterating to fluent, but seeing your answers I think it isnīt possible!!!! thank you, Teresa
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