[FLASH-USERS] Issues with Bondi accretion test of the RadFLAH scheme

[Joaquin Pelle]

Dear FLASH users,

I am currently getting started with FLASH. I am trying to reproduce the radiation-inhibited Bondi accretion test problem of the RadFLAH scheme. The problem corresponds to spherical accretion of matter onto a central luminous object modeled as a point-like source of radiation. The problem is described in detail in Section 4.6 of Chatzopoulos & Weide (2019), the paper about the implementation of the RadFLAH scheme in FLASH.

I am using the latest release of FLASH, and the simulation files under Simulation/SimulationMain/radflaHD/BondiAccretion. My setup command is the one provided in the flash.par file of the simulation directory: 

./setup radflaHD/BondiAccretion -1d -auto +spherical -nxb=16 mgd_meshgroups=1 +parallelio +uhd3Tr IgnoreSpecies=True

When I run the code using the parameter values in the flash.par file as they are (using the physical parameters detailed in the paper), the code crashes before reaching a stationary state (and the analytical solution of the problem). The issue seems to arise due to high-frequency oscillations at the outer boundary which lead to negative internal energies. See the first attached figure below for illustration. For reference, I also attached the log files of this simulation.

On the other hand, I ran another simulation increasing the rho_vac parameter (vacuum density) from its default value (1.0e-18) to 1.0e-16, and the simulation ended successfully, reaching a stationary state, and matching the analytic solution nearly everywhere (aside from a few small features). You can see this final state in the second attached figure.

I also tried initializing the variables from the analytic solution but the high-frequency oscillations at the boundary still apear and make the simulation crash (see the third figure). Lowering the CFL factor down to 0.4 does not help either in any case.

I am a bit lost now as to what could be the source of the problem. I would greatly appreciate any insights or suggestions about things I could try. Please let me know if you would like me to provide any further details that may be useful to diagnose the issue (for example, any other plots or animations).

Thank you very much in advance.   

Best wishes,
Joaquin.
-- 

Dr. Joaquin Pelle
Max Planck Institute for Gravitational Physics (Albert Einstein Institute) 
Am Mühlenberg 1, 14476 Potsdam
Phone: +49 331 567-7168 
Office: 0.28 
Personal website: https://joaquinpelle.github.io/
Institutional website: https://www.aei.mpg.de/person/137090/25873




 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0006.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bondi5.log
Type: application/octet-stream
Size: 6669 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0002.obj>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0007.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bondi.log
Type: application/octet-stream
Size: 2814798 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0003.obj>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0008.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: dens_0181.png
Type: image/png
Size: 34467 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0003.png>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0009.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: density_profile_rhovac_em16.png
Type: image/png
Size: 36094 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0004.png>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0010.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: density_profile_rhovac_em18_analytic_inidat.png
Type: image/png
Size: 34408 bytes
Desc: not available
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0005.png>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20250728/487b750c/attachment-0011.htm>