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Scratch Space Error during combustion simulation

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Old   October 18, 2008, 03:40
Default Scratch Space Error during combustion simulation
  #1
Emmanuel Kasseris
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Hello, I am running a simulation of (premixed) combustion in the cylinder of a gasoline engine.When combustion is turned off,the simulation works fine.With combustion on,however, it fails immediately after combustion begins with this message: *** Scratch unit 78, Failed to find scratch data CELL 1 56 1 1 *** Proc: 1 Error encountered, number: : 549

*** Error 549: Scratch/RAM file failed reading/writing

CELL 1 56 1 1

Most likely cause: full disk or not enough RAM memory

on the system.

If the problem persists contact User Support.

RUN STOPPED !!!

I have 8GB of RAM.Is the scratch space the tmpfs in Linux?How can I increase it? Any help would be much appreciated Thanks
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Old   October 18, 2008, 11:06
Default Re: Scratch Space Error during combustion simulati
  #2
azt
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if you use bash then you can set the tmpdir

ie export TMPDIR='path to temp directory'
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Old   October 18, 2008, 14:55
Default Re: Scratch Space Error during combustion simulati
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Emmanuel Kasseris
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I did and it still fails with the same message.Could it be related to tmpfs and RAM instead of the tmp folder?or my setup? Thanks! Emmanuel
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Old   October 19, 2008, 03:43
Default Re: Scratch Space Error during combustion simulati
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Balduin Bankerotti
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Do you have a 64 bit version of linux and also the 64 bit version of star installed on your machine?

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Old   October 19, 2008, 06:41
Default Re: Scratch Space Error during combustion simulati
  #5
Emmanuel Kasseris
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yes and may I add that this model works fine for cold flow.
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Old   October 19, 2008, 06:48
Default Re: Scratch Space Error during combustion simulati
  #6
Emmanuel Kasseris
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Yesterday I tried setting TMPDIR=a dir with no limit for sure+adding 14 gigs of swap memory (default was 2G and my RAM is 8G) and I restarted the the calc from a couple of time steps before failing...... Still the same error! I am running it now restarting from 200 time steps before failing and monitoring RAM usage closely.It is using almost all of the RAM even before combustion starts...
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Old   October 19, 2008, 09:31
Default Re: Scratch Space Error during combustion simulati
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usker
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What is your grid size, and turbulence model you are using?
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Old   October 19, 2008, 10:40
Default Re: Scratch Space Error during combustion simulati
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c.duckinson
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did you follow the installation notes and set the swap space at least greater or equal than the RAM?
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Old   October 19, 2008, 15:22
Default Re: Scratch Space Error during combustion simulati
  #9
Emmanuel Kasseris
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Initially the swap space was 2G (RAM is 8.2G).But I increased the swap space to 14G using a swap file and restarted the simulation.Same problem...I was actually monitoring RAM and swap space usage before and at the point it crushes (using the free command) and RAM usage was 8 out of 8.2G but swap space usage was only 48 Mb and didn't change as it was crushing, i.e. swap space use didn't suddenly increase...
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Old   October 19, 2008, 15:27
Default Re: Scratch Space Error during combustion simulati
  #10
Emmanuel Kasseris
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around 700.000 cells.K-epsilon turb model with these values: TURBULENCE MODEL ............ => HIGH RE K-EPS MODEL |

| CONSTANTS ................. => C_mu=0.09, C_1=1.44, C_2=1.92, C_3=1.44, C_4=-0.33 |

| => cappa=0.419, Pr_k=1.00, Pr_eps=1.219, Pr=0.90
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Old   October 25, 2008, 17:12
Default Re: Scratch Space Error during combustion simulati
  #11
Emmanuel Kasseris
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It turned out to be a bug in the CFM combustion model!!!!!!!!!! They are fixing it in a patch coming out next week!
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