[FLASH-USERS] The boundary condition of rigid body in the USM MHD solver

[Yigeng Tian]

Dear FLASH users,

I have a question related to implementing a 'rigid body' (i.e. an object
with reflective BC) for the unsplit staggered mesh (USM) MHD solver. It
appears that the BC for B_x and B_z components of magnetic fields (i.e. in
plane components for the 2D cylindrical geometry) are not assigned
appropriately.

I'm running a modified 'laser-slab' simulation using the USM MHD solver,
where I added a strong externally applied magnetic field along the Z-axis
(2D cylindrical geometry) and defined a mesh using the 'rigid body' (take a
look at the init.block file lines 166 - 191).  When the plasma flow reaches
rigid bodies, the simulation stops due to a negative internal energy error.
As shown in the plots below (for B_x and B_z), there are some
abnormal values at the rigid body boundaries.
[image: image.png]
[image: image.png]

It seems that the issue is due to the boundary condition of rigid bodies
for B_x and B_z (but not for Hydro), since the out of plane B_phi component
works fine. So I'm wondering if there is a way to appropriately assign the
B_x and B_z boundary conditions at the 'rigid body', because the FLASH
manual (34.1.2) says "It is possible that the unsplit staggered mesh MHD
solver can support the rigid body but we have not tested yet."

Attached are my Simulation_initBlock.F90 and flash.par files.
Thank you!

Yigeng Tian, Graduate student
Department of Physics and Astronomy
University of Delaware
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20220623/9e700d85/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 188037 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20220623/9e700d85/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 158813 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20220623/9e700d85/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: flash.par
Type: application/octet-stream
Size: 8603 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20220623/9e700d85/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Simulation_initBlock.F90
Type: application/octet-stream
Size: 8553 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20220623/9e700d85/attachment-0001.obj>