[ham551]

I am trying to reproduce a paper that modeled an argon arc jet. However, when just trying to run a base flow (no heat source at constrictor to mimic the arc) I get divergence almost immediately and temperature and pressure go to their limits.

The model conditions:

Density-based solver
2D - Axisymmetric condition
Steady

Energy equation On
Laminar flow

The fluid is Argon using ideal gas for density and Sutherland for viscosity

Inlet = Mass flow inlet at 60 mg/s
Outlet = Pressure-outlet at 0 Pa
Operating pressure is 0 Pa
Walls are no-slip

I think the issue is with the outlet conditions. The paper doesn't give an outlet pressure, they extrapolate it from the inner grid. My understanding is in compressible-flows in Fluent you can't use this outflow condition. However, the flow should be supersonic at the outlet.

Also, no information is given on inlet pressure, so I have set it to 0Pa. I assume this isn't accurate.

Any advice on where I am going wrong and where to improve the simulation?

[LoGaL]

Just think about it man: you are giving at the outlet 0 Pascal, and your operating pressure is also 0, so you are really setting the physical pressure to zero. No wonder everything explodes

[AlexanderZ]

from my point of view:
1. in inlet mass flow boundary you should put the pressure of chamber
2. you may patch chamber with expected pressure
3. you should resolve better boundary layers
4. you may add air domain after the nozzle (extend your domain) so you may use pressure outlet boundary condition there with pressure 0
(in boundary condition you want to put 0 in case your operating pressure is 101315, or otherwise)