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Old   June 20, 2007, 07:05
Default Negative Densities
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Chris
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Hello I am simulating a pulsating(piston) pressure inducer in a closed(no outlet or inlet) system. The pressure should rise from 30 bar to 4000 bar. But after a few time steps the solution stops and gives out the error "negative densities found in more than 100 cells". When I increase the volume of the system more time steps have been carried out, but still the process was aborted! I also recognized that the velocities are negative in some time steps during the compression stroke, which shouldnt be possible!?! Anybody has any advice for me? Would be really grateful for any help!

Greets Chris
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Old   June 22, 2007, 05:36
Default Re: Negative Densities *NM*
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Mike
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Old   June 22, 2007, 05:39
Default Re: Negative Densities
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Mike
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Hi, you are bound to get negative densities with these kinds of simulations. Try using user coded density, since the pressure greatly rises and there may be compressibility issues (for a high viscous liquid).
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Old   June 22, 2007, 07:17
Default Re: Negative Densities
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Chris
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Thx, worked out with high viscosities!
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Old   June 25, 2007, 09:39
Default Re: Negative Densities
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Chris
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Still, does anybody have an advice for the negative Velocities in the compression stroke?????
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