[FLASH-USERS] Question on Implementing Magnetic Diffusion at Lower Boundary (Yl) in 2D Cylindrical Z-Pinch Simulation

[Cunbo Liu]

Dear FLASH developers and users,

I am using FLASH (v4.7.1) to simulate a 2D cylindrical Z-Pinch configuration and trying to implement a return-current structure as shown in the attached figure. In this schematic:
The red regions represent rigid electrodes (treated as solid bodies),
The green region represents plasma,
The blue regions represents vacuum.
The arrows indicate the intended current path.

I encountered an issue where magnetic diffusion seems to only support the right boundary (Xr),  in our setup, the right boundary is blocked by an electrode region, preventing magnetic field from diffusing.
I tried creating a flow-out channel at the lower-right corner, but this workaround yields unsatisfactory results.
I attempted to change the following parameter in flash.par:
diff_magzXrBoundaryType = "circuit" to: diff_magzYlBoundaryType = "circuit"
but the magnetic field did not appear as expected during simulation.

So I want to ask some questions：
Is it possible to enable magnetic diffusion from the lower boundary (Yl) instead of the default right boundary (Xr)?

If yes, which files or routines would need to be modified to support this?

If not, is there any recommended workaround to emulate a return-current structure like the one in our schematic?


Any guidance or pointers would be greatly appreciated.
Thank you for your time and support.


Best regards,
Cunbo Liu


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