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negative pressure & ideal gas equation invalid

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Old   August 21, 2013, 01:11
Default negative pressure & ideal gas equation invalid
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hi all,
i am currently working on an in-cylinder cold flow problem where i am trying to simulate the mesh motion. i am simulating the case only for a 1/8th sector of the chamber. i have 740k elements where its bfc in the moving region and tets in the rigid regions. i initialised the problem with gauge pressure 295725 Pa and reference pressure 0 Pa. the temperature was 407.811 K. while i simulate and plot the static pressure, the values become negative after a few iterations. i tried plotting the temperature, density and pressure to check the validity of the ideal gas equation. when i try to calculate pressure/(density*temperature), its not constant for all time-steps.. need some expert advice on why the ideal gas equation is not followed..
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