[FLASH-USERS] Problem with applyBCEdge

[James Guillochon]

Klaus,

Disabling gravity seems to have gotten rid of the artifacts. I notice from an earlier posting (http://flash.uchicago.edu/pipermail/flash-users/2008-July/002592.html) that you say the grid topology for the multigrid and the grav_boundary_type must match, is the same true for multipole?

The work-around that I see at the moment is to just set the xl boundary to diode and then reset the left-most cells within the actual domain (not the ghost cells) using Driver_sourceTerms, but I would prefer to modify the edge boundary conditions themselves to make things work. Most of the mass in my problem is concentrated at the center of the simulation, the mass from the wind has a negligible contribution. In principle I would want the multipole expansion to ignore everything outside of the box, which is why I chose "isolated."

Thanks for your help, I think I'm getting somewhere now...

-- 
James Guillochon
Department of Astronomy & Astrophysics
University of California, Santa Cruz
jfg at ucolick.org

On Dec 2, 2009, at 10:35 AM, Klaus Weide wrote:

> James,
> 
> Thanks for the additional info.  I still don't have a good idea about what 
> might cause these artifacts, but here are some ideas. 
> 
> It seems you suspect the looping indices in the 
> Grid_bcApplyToRegionSpecialized.F90 file, and maybe you are right, but if 
> there was something wring in the logic there, it should also in other 
> simulations.  Is your setup doing anything that might be a bit unusual?
> For example, are your cell not (logical) cubes of cells? What I mean is 
> NXB == NYB == NZB not true?
> 
> On Tue, 1 Dec 2009, James Guillochon wrote:
>> REQUIRES Driver                                               
>> REQUIRES physics/Hydro                                        
>> REQUIRES physics/Eos/EosMain/Helmholtz                        
>> REQUIRES Simulation/SimulationComposition                     
>> REQUIRES Multispecies
>> REQUIRES Grid/GridBoundaryConditions/OneRow
>> REQUIRES physics/Gravity/GravityMain/Poisson/Multipole
> 
> The combination of the Multipole gravity with your WindTunnel-like BC 
> seems suspicious to me. Are you sure your setup makes physical sense?  
> What gravity boundary conditions (grav_boundary_type) are you using?  
> Whether you use "isolated" or "periodic", my understanding is that 
> multipole gravity is only meaningful if one assumes zero (or near-zero) 
> matter density close to the boundaries.  Which contradicts having an inflow 
> boundary.
> 
> Can you test your setup (at least for a few steps) with gravity disabled,
> to see whether you still have the same kind of artifacts?
> 
> Klaus
> 
> 
> !DSPAM:10135,4b16b3701478854968973!
>