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-   -   Fluent UDF's / dynamic meshing errors (http://www.cfd-online.com/Forums/fluent/38329-fluent-udfs-dynamic-meshing-errors.html)

Peter October 21, 2005 06:35

Fluent UDF's / dynamic meshing errors
 
Good morning all

I am trying to model an aerofoil starting motion abrubtly. I have written a UDF which basically says

if time < t1 then velocity = 0 else if time < t2 then velocity = x else velocity =0

so that should start off with nothing moving. The aerofoil should then move a short distance and then stop.

The problem is, when I try to run the problem, I eventually get an error message. Sometimes this is 'Segmentation violation', sometimes 'Bus error'.

I have a feeling that this is because the remeshing process cannot cope - sometimes the error is due to negative cell volumes.

Can anyone give me a hint as to how I can solve these problems? Or if anyone can think of an easier way to model the problem, that too would be helpful.

Thanks all,

Peter

Peter October 21, 2005 10:12

Re: Fluent UDF's / dynamic meshing errors
 
I think I found the solution. Playing around with the dynamics mesh parameters - especially minimum and maximum cell volumes - and using very small time steps (~0.005s) seems to elimate the problem.

Peter

gaohongliang November 6, 2005 04:36

Re: Fluent UDF's / dynamic meshing errors
 
I think you should apply for DEFINE_CG_MOTION ,The model might be useful for you


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