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Old   March 22, 2004, 08:48
Default -Nan- error
  #1
cfdguy
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Hi all, I am simulating a case with thermal radiation, velocity and pressure BCs, High Re turbulence model. The case is transient. Model contains hexa, piramid, tetra elements. My run is coming out with -Nan at TKE and dissipation residuals. I tried giving steady state results as initial guess but still it fails. My PISO correctors are not exceeding the 20 limit. What could be the reason? Thanks in advance.
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Old   March 22, 2004, 13:01
Default Re: -Nan- error
  #2
roadracer
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Turbulence values at boundaries?
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Old   March 23, 2004, 01:19
Default Re: -Nan- error
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cfdguy
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Thanks roadracer. But how to see where it is giving error? Is case.div useful? thanks again.
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Old   March 23, 2004, 04:02
Default Re: -Nan- error
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Richard
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The .div file is very useful: just post-process it like a .pst file. This will hopefully show you where the problem lies in the domain. The NaNs suggest there is maybe a division-by-zero or something like that in the code. Something the STAR developers didn't expect to be zero - as roadracer said, turbulence at boundaries could be one thing. Also initial conditions for turbulence.
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Old   March 23, 2004, 14:05
Default Re: -Nan- error
  #5
paul
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You might also want to check if there is a zero edge length in one of your cells.

NAN's are hard to find, good luck.
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Old   March 24, 2004, 04:36
Default Re: -Nan- error
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cfdguy
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HI, I have successfully run the steady state case on the same mesh and I think there is no problem in the mesh. problem is occuring only in transient case. I am looking at the initial condition of the turbulence or its location. Thanks,
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Old   March 25, 2004, 01:33
Default Re: -Nan- error
  #7
cfdguy
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I tried a lot to start the run but failed. Actually I don't want to simulate transient flow(velocity), but only variation of temperature with time. Velocity being constant with time. How to do that? If I give velocity BC by nrmal way, it simulates the velocity also with reapect to time. Kindly help.
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