Petra Without going into the details of the issues you are encountering:
Accretion onto a black hole has a near-spherical or axisymmetric symmetry. In my experience, this is better modelled using a multi-block structure than mesh refinement. Are you aware of <http://llamacode.bitbucket.org>? -erik On Wed, Mar 9, 2016 at 10:10 AM, Petra Suková <[email protected]> wrote: > Hello everyone, > > I am a postdoc at CFT PAN Warsaw and a relatively new user of ET. I am > trying to use ET for simulating accretion of low angular momentum magnetised > gas onto Kerr black hole. > > I use GRHydro and GRHydro_Init thorns on stationary Kerr spacetime. Using > mesh refinement with nonzero magnetic field always leads to crash of the > computation, after few hundreds or thousands of iterations. It looks like > the cause of the crash is violation of divB=0 constrain in the buffer zones > on the edge of refined level, which grows and later starts to propagate into > the grid. > > More details: > I have adapted GRHydro_BondiM.c and run some tests with low angular momentum > accretion, B=0, spin=0 and several refinement levels, which after some > modifications worked quite well. Now I am trying to include magnetic field. > I have set initially vertical magnetic field. After first iteration, divB in > the buffer zones increases to values around 10e-7 and it is growing during > the evolution. After some time (depending on the Bfield strength, grid size > etc, typically tens or hundreds of M), the values of divB in the buffer > zones exceed 0.1 and start to spread inside the grid zones and spoil the > simulation. > I thought, that maybe some of my changes caused this, so I tried to run an > example par file MBondi_B5.70_Mdot12.57_Npts100_Sch.par with clean ET > release 12, but that crashed immediately in the first iteration. So I tried > to lower bondi_bmag from 5.7 to 0.1 and this worked and was stationary, but > it runs only on unigrid without refinement. When I added the mesh refinement > and fixed GRHydro_BondiM_Boundary to not act on the refinement boundary, the > same problem with buffer zones appears. I am attaching the par file of this > computation together with few snapshots of divB, rho and Bvec. > My guess is that during the prolongation and restriction of magnetic field > vector the DivB=0 condition is violated and this error is continuously > increasing when the Bfield and matter is accreted through the refinement > boundary. > Has anyone faced similar problem? Or does anyone have some working parfile > with similar computation with magnetised gas and at least two refinement > levels, which he can send me? I could test that and hopefully discover my > problem. > > Thanks a lot, > Petra > > --- > Tato zpráva byla zkontrolována na viry programem Avast Antivirus. > https://www.avast.com/antivirus > > _______________________________________________ > Users mailing list > [email protected] > http://lists.einsteintoolkit.org/mailman/listinfo/users > -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/ _______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
