[Felixx]

Hello everyone,

I am pretty new to StarCCM+. For my project, I have set up a reference case, where I transiently simulate an ideal gas in a 2D closed box with constant volumetric energy source option.

My setup is: coupled flow and energy, gas, gradients, ideal gas, implicit unsteady, laminar, two dimensional.

As I would expect from ideal gas law and conservation of mass, the pressure inside the box should proportionally increase with temperature. However, the pressure is not changing. I only see an increase in temperature and a decrease in density. The latter violates conservation of mass in my opinion.

I also tried a few other setups:
1: constant density to force density to be constant. Here, the temperature increases, but the pressure doesn't change. It seems like pressure is not calculated at all. When I calculate p=rho*Runi/M*T with surface averaged values for rho and T, p increases linearly as expected.
2: seggregated solver: no changes.
3: reference pressure set to 0 Pa and initial pressure to 1 atm: no changes.

The fluid is not moving at all (only in orders of E-16 m/s), as I would expect, since I have not included boyancy. Does anyone know, where the problem lies and how to setup the model properly?

Best regards and thank you in advance,

Felix