# a problem with UDF

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 July 24, 2003, 15:48 a problem with UDF #1 Baz Guest   Posts: n/a Hi, I have a problem with interpreted UDF . I wrote a simple initialization function for density gradient and after I initialize the solution, I can see contours of variable density. But, even after one iteration the density changes into constant. Why? Thank you for help.

 July 24, 2003, 22:56 Re: a problem with UDF #2 ccc Guest   Posts: n/a hi, I have similar problems. if anyone know, think in advance.

 July 25, 2003, 05:12 Re: a problem with UDF #3 Ale Guest   Posts: n/a Hi, perhaps I didn't get the point, but that's what I think: If you initialize a variable, however you do that, you give an initial approximation of the solution. If your model doesn't change the density during the calculation, and you've set a constant value for density in the Materials panel, at the second iteration you'll get that value in all the domain. You should probably write a DEFINE_PROPERTY macro in your UDF, defining the law of change of your density during the simulation. Good luck, Ale

 July 25, 2003, 09:53 Re: a problem with UDF #4 ap Guest   Posts: n/a I agree with Ale. If you keep constant the density in Material properties, FLUENT will use your initialization value just to compute the first iteration. Hi ap

 July 26, 2003, 18:39 Re: a problem with UDF #5 Lola Guest   Posts: n/a I thought after 'first iteration', the solution is NOT 'converged'. Why would I bother checking any solution in some intermediate iterations??

 July 27, 2003, 19:22 Re: a problem with UDF #6 ap Guest   Posts: n/a I'm not telling the solution is converged after the first iteration. I just say that if you initialize a density value, but you keep constant density in the material properties, FLUENT will use the value specified there (Material properties) to do all computation except for the first iteration. Hi ap

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