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Prateek garg November 6, 2012 06:56

Mixing Problem and hardware issue
Hi friends,

I am trying to simulate mixing of air and kerosene (gas phase) in CFX in a cylindrical tube. My grid contains 3 million cells but it can only solve around 400 iterations per day. When I checked the CPU usage its only 6-10 percent. However, I am using 7 partitions while solving the problem, my CPU comprises of 16 threads i.e. 2 octa core intel xeon processors. When I use more than 7 partitions my Simulations stops saying error Return code 1 . I cant understand what is the problem and want to know if I can use more partitions? If yes why my simulations is stopping with error?

Please Help!!

alquimista November 6, 2012 07:41

Hi Prateek garg,

Can you provide more information? Such as OS, specification of the computer and the .out file of CFX with and without error?

If you have 12 cores and available license to run the case (maybe you need more HPC licenses) then you can run it.

Prateek garg November 6, 2012 07:55

Hi alquimista,

I am using windows server r2 HPC 64 bit with 16 GB RAM , 2 intel xeon Octa core processors i.e. i have 16 cores.

alquimista November 6, 2012 08:08

The run generates a .out file can you paste the last lines before crash?

Also, there is a limited number of license to use different cores. If you are not sure about it... in the Client ANSLIC_ADMIN Utility:

View Status/Diagnostic Options => Display the license status

And check for something like:

Users of acfx_par_proc: (Total of 8 licenses issued; Total of 0 licenses in use)
Users of acfx_parallel: (Total of 8 licenses issued; Total of 0 licenses in use)

alquimista November 6, 2012 08:16

Be sure that you don't have multithreading enable in your computer, if not you will be using 7 threads of 32 available.

Prateek garg November 6, 2012 08:50

1 Attachment(s)
Nov 06, 2012 18:12: Attempting to display the license status...

================================================== ===========

ANSYS Licensing Interconnect path =

ANSYS FLEXlm license path =

***** Note: Due to a FLEXlm limitation, all tasks may not be found *****
__________________________________________________ ___


lmutil - Copyright (c) 1989-2009 Flexera Software, Inc. All Rights Reserved.
Flexible License Manager status on Tue 11/6/2012 18:12

[Detecting lmgrd processes...]
License server status: 1055@License
License file(s) on License:

lmgrd is not running: License server machine is down or not responding. (-96,7:11004 "Comm. error")

================================================== ===========
please find attached out file and above is the license status my system is still running a simulation and i use institute's license

alquimista November 6, 2012 09:18

I don't know why your license server seems to be down. But anyway the run starts solving so there's not a license problem.

I would suggest to check if it also happens running any .def present in the ANSYS folder (i.e.: C:\Program Files\ANSYS Inc\v130\CFX\examples). As far as I understand it is not clear if the problem is related with the case (overflow is present) or it is a system problem.

I'm a Linux user and maybe I'm missing something...

evcelica November 6, 2012 17:49

It looks like you are doing a VOF model? Sometimes with these models if one of your partitions falls along a sharp contour (where your air/gas are mixing) This can lead to overflow errors. I had the same thing happen to me in a tank sloshing model where one of the partitions was along the liquid/vapor line. You can either partition your model so this doesn't happen, or use less cores to reduce the number of partitions.
I'm not 100% sure this is your problem, just my best guess.
If you are only using 6-10% of your CPU you may be running out of RAM?
A 16 core computer with 16GB RAM sounds a little wierd, what CPU model are they? Is hyperthreading disabled?
Also running more than 8 cores is not going to give you much speedup since CFX is limited by memory bandwidth. On large models I get the same performance with 4 cores as I do with 6.

Alquimist had a pretty good idea with testing other examples, you could also run intel burn test or prime95 to check for hardware errors/stability.

Prateek garg December 13, 2012 14:39

Igniting Mixture
Hi All,

Thanks to all of you for you response. I have done with mixing now there is real problem as I want to ignite the mixture. I want to know how can I use these obtained mixing results to ignite the mixture.
I want to patch my domain with high temperature to ignite the mixture but what I want to know is do I need to create another .DEF file and set the case as required for ignition by setting combustion model and reaction?
If it is so, then I would have to define material for combustion but since I already have mixture in my domain, how could I define the new material(mixture)?

Please Help!!

ghorrocks December 13, 2012 17:30

There are a few CFX tutorials which use combustion. Have you done these tutorials?

Prateek garg December 14, 2012 01:16


I have done combustion earlier but haven't gone through any tutorial showing how to connect your previous results with new simulation. Can you specify any particular tutorial that is related to my problem.

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