Varying mean free path

General discussion
1

Hi,

I wanted to see if there was a way to have a spatially varying mean free path. For example, if I want to simulate the flow particle A in a pipe with pressure gradient of a background gas, the mean free path will change with the pressure along the pipe. From I can tell, you can only prescribe one mean free path for a simulation; is that right?

Thanks,
Vic

2

Molflow doesn’t support partitioning the volume, as only the walls of the geometry are imported. The only workaround, that we thought of before, would be to use the already existing structures and link facets, which would allow to assign different MFP to different structures. What experiment or physics would require a gradient of background gas and particle scattering?

3

I’ll give that a try, thanks! I’m wanting to quantify the scattering of the simulation particle in a volume with a pressure differential of the background gas.

4

Hi Marton,

To follow-up, when I try to change the background gas for a structure, those parameters are set for the other structures as well. So if I set the mean free path in structure 1, then set the background gas parameters in structure 2 to, when I go back and check the background gas parameters for structure 1 they’re the same values as I just input for structure 2.

5

Sorry if my message wasn’t clear, the per-structure background parameters are not implemented, it’s a development idea for the future. Currently gas parameters are global.