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DISS causes simulation to diverge

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Old   October 21, 2005, 05:27
Default DISS causes simulation to diverge
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Cb
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Hello everyone

I am trying to run an unsteady flow in a simple volume - an inlet pipe and an outlet pipe connected to the same face of a cubic volume. I am using a pressure pulse as defined in a .dat file as my pressure inlet, and outlet pressure is constant at zero.

I know the boundary conditions are ok, because I have 3 different variations of my simple simulation and the first two converge easily. However, this simulation diverges at timestep 1 with DISS at 5.51E+17 and ENTH at 2.95E+05. All other residuals are 0.00E+00

When I run it as laminar it diverges at timestep 2, but the residuals are all 0 so I don't know what causes it.

Does anyone have any ideas?
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Old   October 21, 2005, 05:45
Default Re: DISS causes simulation to diverge
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carno
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try reducing the pressure under relaxation factor. say 0.8. default is 1. check whether PISO correctors are reaching to its limit and courant number (normally 100).
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