[simulant1]

Hello,

I am simulating an isochoric process:
- Closed Cube (4 wall boundaries, as I am doing a 2D-simulation)
- Gas (Air) filled
- Heated by the walls from 300 K to 400 K
- No velocity profile, only natural convection

For this case, the volume and the mass is constant. Therefore, the average density in the cube is constant. Because of the Ideal Gas Law, the pressure should rise with the temperature rise of the gas. But in my simulation, only the density changes (which is physically total wrong), but the pressure stays almost constant. Also, if I change the thermal conductivity of the gas, the value of the pressure at the end of the simulation is completely different, which is totally wrong. Thermal conductivity only affects, "how fast" heat is transferred trough the gas, but does not affect the pressure level at the end of the simulation.
This all happened, while I was using the Coupled Solver. Yesterday I switched to the Segregated Solver and now everything is fine. All of the problems from above are fixed and the pressure rise is corresponding to p2/p1 = T2/T1 (Ideal Gas law for an isochoric process), while the average density in the volume is constant.

Did I find a bug in the coupled solver? Because I think, the different solvers only change the way, how the equations are solved, but should not effect the results on the whole (especially not in that extreme way, it does here).

Best regards