I've worked on CFD for a capillary to diverging electro spraying from ambient nozzle spraying to a ion funnel under vacuum. Since I am hindered by computational power, I avoid making my flow go through a small 0.015 in inner diameter (ID) capillary and begin the simulation as the ideal gas reaches the diverging nozzle.

My current set up involves these boundary conditions

1. Mass-flow-inlet 0.015 inch diameter entrance at (X)kg/s mass flow and the Supersonic/initial Gauge Pressure at choke flow pressure for ideal dry gas (408 torr). Direction Specification method is "Normal to boundary". Nothing else was altered.

2.Pressure Outlet at a Pump in the South side of the instrument that pumps gas out towards the back of the funnel. The Gauge Pressure is set to 0.1 Torr at this exit.

The pump in use is an E2M80 with Ultimate Vacuum at 7.7 x 10-3 Torr. If anyone could shine light on a way to calculate the pressure of the pump at the entrance of the chamber (2 inch diameter pump out) it would be better then my current educational guess. Nothing else was altered.

3. Pressure Outlet at the end of the cone's tapering nozzle. Here the pressure gauge was set to 0.05-0.07 torr since the physical pressure gauge in the next chamber reads 5mtorr on average. Nothing else was altered.

Im aware I only did a few iterations, but I have made made 10,000 iteration simulations before in the same set up and it always diverges eventually and never reaches a steady jet.

tl:dr

I am attempting to recreate a FUNPET w/ Jet Disrupter set up as seen in this paper:

DOI: 10.1007/s13361-018-2038-3

"interface 4"

However, my simulation continues to diverge due to my boundaries. Does anyone know a better way to se it up or am I misinterpreting something? This is my first time ever working with CFD or any form for Computational chemistry work so apologies for my lack of understanding.

Thank you,

Erick