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Old   December 18, 2000, 10:49
Default negtive density
  #1
zliu
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Trying to run transient analysis, the run stop after

the first iter. message is like

STEP UVEL VVEL WVEL MASS T EN DISS ENTH U V W P TE ED T

1 1.93E-02 2.41E-05 6.43E-02-4.74E-02 9.69E-01 7.81E+03 1.36E+04 -1.86E+00-6.49E+00 1.63E+02 1.28E+03 2.24E+02 1.99E+06 6.02E+02 Warning - starwatch daemon is not registered, no information sent to starwatch.

*** ERROR #076 *** NEGATIVE DENSITIES FOUND AT MORE THAN 100 CELLS. RUN STOPPED

what wrong of my model set-up
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Old   December 18, 2000, 11:04
Default Re: negtive density
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Durstberger
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Hi

Does your time step meet the courant equation?

(Cr = (v * t)/L ,where Cr = Courantnumber of a cell, v = velocity of fluid in this cell (compressible: velocity of fluid + speed of sound), t = time step and L is the length of this cell)

The max. Cr shouldn't exceed 50 - 100.

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Old   December 20, 2000, 05:29
Default Re: negtive density
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Ahmed Hassaneen
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If you do have moving mesh (events module) you may try to reduce the time step length.
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Old   December 20, 2000, 05:33
Default Re: negtive density
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Ahmed Hassaneen
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Another thing to you and to the others who has the same problem you may try the MARS differencing scheme and don't ask me why because I don't know why but it works.
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