[FLASH-USERS] 2D +spherical point mass AND self-gravity question

[Norbert Flocke]

Hello Ivo,

The new multipole solver does NOT support additional point mass. This is a 
feature that remains to be implemented. The old multipole solver does 
support an additional point mass, however the old code is outdated and has 
some numerical flaws, so you have to use it at your own risk. I think that 
Sean Couch (at Caltech right now) implemented his local version of the new 
multipole solver with additional point mass as an option, so probably you 
should contact him. Right now I simply don't have the time to add this 
additional feature to FLASH's official new multipole solver. Maybe in the 
future sometime, when my workload is a bit less and there is sufficient 
demand for the point mass option.

Best regards,
Norbert


On Tue, 5 May 2015, Ivo Seitenzahl wrote:

> Dear FLASH-users,
> I have run into a problem with the gravity for my problem. The geometry is 
> +spherical and dimensionality is 2D.
>
> What I've been trying to set up is self-gravity (as far as I can tell only 
> multi-pole is supported in 2D+spherical) IN ADDITION to a single central 
> "point_mass".  Essentially what I have is a central compact object (think of 
> it as a black hole) surrounded by a self-gravitating envelope. So a further 
> complication is that xmin > 0.0 (I have excised a central region from the 
> computational domain, still, so the point_mass would sit outside the 
> computational domain).
>
> Looking here it seems to me that Poisson gravity and point_mass is a valid 
> combination.
> http://flash.uchicago.edu/site/flashcode/user_support/rpDoc_4p22.py?submit=rp_Gravity.txt
>
> However, it seems to be a strict requirement (by that the grid should begin 
> at r=0 (i.e. xmin=0), which is communicated clearly as an ERROR by 
> gr_mpoleInit.F90 if I build the problem with +newMpole.
>
> *****
>  if (radialXGrid) then
>      if (gr_mpoleDomainXmin /= ZERO) then
>          call Driver_abortFlash ('[gr_mpoleInit] ERROR: radial X-coord out 
> of range')
>      end if
>  end if
> *****
>
> Am I just SOL or am I missing something? If anyone has any insight how to 
> setup self-gravity in 2D+spherical (with xmin > 0.0) and a central (fixed at 
> the origin) point mass then I would greatly appreciate any suggestions/help.
>
> Best wishes from Down-Under,
>
> Ivo
>