Question about unusual physical behavior of the MHD jet

[mgomezpico-ETSIAE-UPM]

Good morning everyone,

I am an aerospace engineering student at the Polytechnic University of Madrid, currently working on my Bachelor’s Thesis on MHD jets using Athena++.

When simulating the jet, after enabling the magnetic field and the HLLD solver via configure.py, and using the default boundary conditions and problem setup (only modifying rjet to 0.5), I observe an strange behaviour of the flow. It seems as if there might be some numerical or physical instability.

I have performed a convergence test to check whether this could be related to grid resolution or the CFL condition, but it does not appear to be the case.

Could anyone help me understand whether this behavior is expected, or what might be causing it? I have attached a screenshot of the flow at timestep 150.

Thank you very much!

[tianninglyu]

Hi,

I just see this discussion, and I think your problem might be similar to what I have run into about 3 yrs ago. I think our discussion might help you: #514

Best regards,
Tianning

[mgomezpico-ETSIAE-UPM]

Already solved... but thank you! It was the boundary condition which was giving problems...

[tianninglyu]

Wow, could you please tell me more details? I'm really curious about that. Thanks!