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November 11, 2009, 10:07 
Error message CFX Solver

#1 
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Location: Norway
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Hi.
The solver stopped my simulations after appr. 15 timesteps given the following error message: An error has occurred in cfx5solve:     The ANSYS CFX solver could not be started, or exited with return   code 255: . No results file has been created. Does anyone know what "return code 255" mean? 

November 19, 2009, 06:38 

#2 
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Bruyère
Join Date: Oct 2009
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Hello Fatnes,
does your .out files contain some warnings? could you send an extract of your .out file (max 97 kB)? Bye 

November 20, 2009, 03:13 
another error

#3 
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I don't even get a .outfile. Error message is "The CFX solver for system 'modelname' did not produce a results file. No output is available. Cell A5"
Any ideas? 

November 20, 2009, 03:37 

#4 
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I've talked with ANSYS Support and they can't help much about the error code. According to them their error codes are very general. In my case the solver runs smootly, converging within the first coeff. loop in every timestep, but suddenly it get convergense problems. After a few timesteps the solver stops with the following message (see attachment)


November 20, 2009, 06:00 

#5 
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Bruyère
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Hello,
It could be a problem of memory : what is your physical memory on which type of machine? example : Linux with 2 Dual core (2.4MHz) 8GB ram : could you tell me what are the characteristics on your machine and what kind of calculation are you running : is it a parallel local PVM methode ? with how many partitions? And during the 15 Timesteps look at the memory used by your solver? How much? Bye Bye 

November 21, 2009, 12:37 

#6 
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255 may be some network error with parallelization. If you start a second run with exactly same settings, crashes again?


November 23, 2009, 14:30 

#7 
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mohsen
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Posts: 53
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hi dears
i have this error too.my hardware is: 4 Gb ram  cpu: intel quad 4000 it worked correctly.but i dont know that why this erro occurs. 

November 23, 2009, 14:46 

#8 
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mohsen
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i thought the error be due to runing the simulation with previous parameters.
i changed inlet boundry condition but dont solve this error. this error is displayed when out file comes to "solve" in cfxsolver monitors i was ran this simululation with mpi parallel method but now this error occurs how can solve this error below posts display my simulation information please remark Last edited by mehrdadeng; November 23, 2009 at 16:53. 

November 23, 2009, 16:57 

#9 
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mohsen
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this simulation is consist of 2 domain .blade domain(az immers domain) and housing domain(az fluid domain)


November 23, 2009, 17:05 

#10 
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mohsen
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domains parameters:
further more i tested solid domain instead of immerse domain but occurs above mentioned error 

November 23, 2009, 17:09 

#11 
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mohsen
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housing doman information:


November 23, 2009, 17:15 

#12 
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mohsen
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inlet boundry condition:
inlet and outlet boundry condition has been defined on housing domain(fluid domain) 

November 23, 2009, 17:21 

#13 
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mohsen
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outlet boundry condition and solver control parameters:


November 23, 2009, 17:23 

#14 
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mohsen
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how can solve this problem?


November 23, 2009, 17:35 

#15 
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mohsen
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messages that have been appeared in cfxpre.i dont know couse of this messages because i defined only rotation for immerse domain but message says that ...


April 9, 2010, 17:28 
the same problem

#16 
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nazareno mancinelli
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Location: argentina
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i'm having the same problem. with the same sign. i start running a case and i saw all the monitors decreasing smothly....but in any time the cfxsolver stop with this 255 error code.
i think is a strange error, because if i change an imput parameter just a little (ie: 4 to 5 m/s inlet, or 100 to 105 rpm) the solution converge. so, i try changing some parameters. but i know that this is not the solution of this problem.... can you fix it? regards 

April 10, 2010, 07:36 

#17 
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Glenn Horrocks
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It almost certainly means the solver has diverged. In fact the divergence is bad enough that it got a divide by zero error and crashed the solver. You will need to improve the numerical stability of the solution.


August 29, 2010, 11:44 
Same problem here

#18 
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compFrac
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I am doing flow analysis of a mixed flow compressor. It basically has a centrifugal impeller. I get the same error code 255 with no output file generated.
Only the 'dx' and 'dy' comes in the equation. If a divide by zero error comes, the problem should lie in the meshing. Any other suggestion??? If a divergence comes, the design values may not be right... A few changes should rectify the problem. But my problem is that, with the same design values, i can generate results in fluent... why not in cfx... And what exactly is this error??? The above mentioned posts are not much convincing 

August 29, 2010, 19:30 
Problem resolved

#19 
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compFrac
Join Date: Aug 2010
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In my case of mixed flow compressor, i had to entered mass flow rate through out the coImpressor. Instead i had to enter flow through the passage.
eg: no. of blades  22 total mass flow rate  2.7 mass flow per passage  2.7/22 with all the other conditions correct, the heavy mass flow rate of 2.7 per passage, was reducing the numerical stability of the problem. Considering the CFD equations for turbo machines, the mass flow rate comes along with the constants. This error has made the numerator very high and denominator remains very small for fine meshing; resulting in high divergence of the equations. So, the software gave me an error code 255, terminating the iterations. This error should be because of huge divergence. Not necessarily divide by zero. error code 255 in cfx is caused due to numerical instability of the equations. The above post is right. But many meanings are there to numerical instability. Since every case is different 

September 24, 2010, 05:31 

#20 
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I have the same error while modeling reacting flow for coal gasification. Slight change in mass flow rates leads to crush. After changing parameteres to previous values (or much higher values) CFX cannot converge. In my case calculations are terminated at 79th iteration


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