[FLASH-USERS] multigrid in 2-D

[turcotte]

Hello all,

I have been trying to use the multigrid solver for gravity in 2-D
and have have had difficulty making it work well.

I have a cartsian grid set up with a small "star" with the rest of the domain 
filled with low density "circumstellar" matter. I eventually have inflowing 
matter from one edge of the domain.

If I define grav_boundary_type as "isolated" the code crashes in 
gr_isoMpoleInit  because it is trying to use the multipole solver that does 
not work in 2-D cartesian.

If I define grav_boundary_type as "periodic" the code crashes and I get the 
following error message:
gr_hgMapBcType: An unexpected gr_hgBndConditions was requested for the WORK arr
 ay:           1         -32 
 
Now I have managed to make it work if I use grav_boundary_type = "periodic"
and if I short-circuit gr_hgMapBcType by adding 
  bcTypeToApply = GRIDBC_MG_EXTRAPOLATE
  return
at the top of the routine before anything else is executed.
No crashes and the code seems to be doing the right thing eventually (the 
potential looks right) but the potential is not ok during the first 
several time steps. There are strong features in the gravitational potential at 
the boundaries that vary strongly with time.

Apart from the problems at the start of the run it seems that there should be a 
better way of doing things!

Thank you for any ideas!
And belated thanks for all who have helped in the past!
Sylvain
 

Sylvain Turcotte
Physics Department    turcotte at apollo.ubishops.ca
Bishop's University   tel: (819) 822-9600 x 2287
Lennoxville (Quebec)  fax: (819) 822-9661
Canada  J1M 1Z7       office: J 11B
URL:  http://apollo.ubishops.ca/~turcotte