[gustavosimiema]

Hi,

I´m trying to simulate the gas (O2 + N2) flow inside a low pressure chamber. In this moment I´m not interested in reactions.
I´m using steady state, laminar model (Low Pressure boundary slip), activated energy equation and species Transport (inlet Diffusion, Diffusion energy source, Thermal Diffusion enabled).
Operating conditions - 1Pa
inlet (mass-flow-rate) = 4.26e-6
outlet (pressure-outlet) = 0Pa

When I start Simulation the message error appears "Error: Divergence detected in AMG solver: x-momentum" and I´m not able to solve it. I tried to reduce the Relaxation factors... but didn´t worked.

Anyone has a hint?

thanks in advance

[CFDYourself]

try the following:

- don't use mass flow; stick to velcity inlet and pressure outlet. do a back-of-the-envelope calc to find velocity from continuity.
- don't mess with the URFs justnow; stick to the defualt settings.
- don't start with mixtures; start with the defualt air.

keep going more and more simple until it works. also, could be an issue with the mesh. have you named the inlet & outlets etc ?

[gustavosimiema]

Thank you so much for your suggestions. I will try it and let you know. Regarding your questionar I named The outlet and outlet. Should I named walls too?
How can I find The velocity from The continuou equation using mass flow rate?
The Knudsen number is 0,038

Thanks

[CFDYourself]

Hi gustavo,
sorry, I shouldn't have called it a "continuity equation", the term is ambiguous in this context.

I meant:
Q=rho*u*CSA
mass fr = density * velocity * cross sectional area for flow.

and rearrange for velocity.