Discussion Forum

I am trying to simulate my cryo chamber vacuum system that is being flooded with neon. I know based on my calculations that the Knudsen number places this within the transitional flow regime, which is why I am modeling it as such. However, when I set all of my parameters, it will not converge, and I was hoping someone more experienced in COMSOL can help. Here is a list of the parameters and geometry I'm using: 1. It is a 2D simulation with a simple symmetric design, see attached

2. Material used - Neon. (this is modeled correctly based on other simulations I have run using neon)
3. Flow Properties: a. T = 25K, Pa = 3.45Pa, Mean molar mass = 0.02018 kg/mol
4. Outgassing Wall: Molecular Flux 1e23/(m^2s)
5. mesh: coarse

When I decrease the outgassing wall's molecular flux to 1e20, it will converge, but anything above that will cause it to fail. If i check the "Neglect scattering term" box, it will also converge with decent values, but I feel like this neglects the physics I'm looking for. I am expecting a number density of about 1e16cm^(-3), which is how I know it simulates it correctly. I have also tried to creating an inlet with the flow rate set to the proper velocity, but that gives me values that are off by more orders of magnitude than I care to post. Is there a different solver I should be using? Am I modeling this correctly? I modeled it first using the molecular simulation solver, which gave some successes, but I’m really hoping to get this to run. Any help will be appreciated.