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-   -   Floating Point Error for Mixing Plane Model (http://www.cfd-online.com/Forums/fluent/32248-floating-point-error-mixing-plane-model.html)

Lee October 2, 2003 23:43

Floating Point Error for Mixing Plane Model
 
Hi,

I am doing some turbomachinery simulation with Mixing Plane Model. Anyone know the reason why I have the floating point error after few iteration?

I already lower the under-relaxation value and changed geometry couple of time.

Thanks!

thomas October 3, 2003 09:57

Re: Floating Point Error for Mixing Plane Model
 
Hello. If you are using a UDF check if you do not have a division by 0. Thomas

Lee October 3, 2003 11:16

Re: Floating Point Error for Mixing Plane Model
 
Hi, Thomas, Thanks for reply.

I could not really understand. Would you mind to explain to me in detail how to check where the problem is?

Thanks again.

thomas October 3, 2003 11:27

Re: Floating Point Error for Mixing Plane Model
 
Well I am assuming you are using a UDF. What I mean is really often when people creates UDF they generally forget that for the first iteration some variable can be zero. Therefore if you are divided a number by zero your solver will blow up telling you 'non floating error'. 'non' means 'not a number'. Depending on your UDF this kind of error does not effectively happens at the first iteration. An example, if you are simulated a domaoin with a stagnant water as initial condition and you are calculated for the first iteration something like 1/Re therefore lets call it BOOM !!! because Re=0 . To find this kind of think there a simple way : reread your UDF.

All that is just a suggestion, it might that or something else I do not figure out yet. cheers thomas

Andy October 6, 2003 10:27

Re: Floating Point Error for Mixing Plane Model
 
I've had similar problems recently with floating point errors on a multi processor simulation of something fairly complex, but with no UDF's, just a mixing plane alone.

The solution for my problem seems to be to run on a single processor, where it runs fine....?

Any and all suggestions gratefully received!

Lee October 6, 2003 19:38

Re: Floating Point Error for Mixing Plane Model
 
Thanks,

I am not using UDF.

thomas October 7, 2003 05:29

Re: Floating Point Error for Mixing Plane Model
 
Hey, I remember one day I got that case because I have made a mistake in boundary conditions. I mean in my case I had set a wall boundary condition instead of an axis boundary condition and then FLuent refuses to calculate telling me 'floating point error'. Maybe it could help you.

thomas


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