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Scratch Space Error during combustion simulation |
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October 18, 2008, 04:40 |
Scratch Space Error during combustion simulation
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#1 |
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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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October 18, 2008, 12:06 |
Re: Scratch Space Error during combustion simulati
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#2 |
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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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October 18, 2008, 15:55 |
Re: Scratch Space Error during combustion simulati
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#3 |
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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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October 19, 2008, 04:43 |
Re: Scratch Space Error during combustion simulati
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#4 |
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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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October 19, 2008, 07:41 |
Re: Scratch Space Error during combustion simulati
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#5 |
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yes and may I add that this model works fine for cold flow.
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October 19, 2008, 07:48 |
Re: Scratch Space Error during combustion simulati
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#6 |
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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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October 19, 2008, 10:31 |
Re: Scratch Space Error during combustion simulati
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#7 |
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What is your grid size, and turbulence model you are using?
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October 19, 2008, 11:40 |
Re: Scratch Space Error during combustion simulati
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#8 |
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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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October 19, 2008, 16:22 |
Re: Scratch Space Error during combustion simulati
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#9 |
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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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October 19, 2008, 16:27 |
Re: Scratch Space Error during combustion simulati
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#10 |
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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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October 25, 2008, 18:12 |
Re: Scratch Space Error during combustion simulati
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#11 |
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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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