Negative absolute pressure for material model
I am trying to simulate a model similar to Ideal Gas Compression in an Actuating Piston . My velocity value is higher than what is being run in the example.
When i run the model for 2.5 m/sec velocity ,i get the error *** ERROR: Negative absolute pressure for material model <air> . However on reducing the velocity to 0.025m/sec, the model runs. I am confused why this happening.
PS: I am using ideal gas for air.
Answers
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Typically these negative pressure and/or negative temperature errors happen when the boundary condition or initial condition values are not consistent with the ideal gas density being a function of absolute temperature and absolute pressure. For example, typically the outflow condition is pressure = 0. But for ideal gas density, you may need to use pressure = 101325 instead. Etc.
Or sometimes the initial conditions may not be close enough to a physical state that the pressure goes negative and causes failure. You may need to run first with constant properties and correct boundary conditions to establish a reasonable flowfield - then do a restart with ideal gas density.
If you can attach the .inp, please do so.
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