Hi Roland, > I generally suggest shifting the grid so that the closest gridpoint > > to the origin is (dx/2, dy/2, dz/2), where dx,dy,dz are the > > resolutions on the finest grid. I've used this trick many times to > > stabilize evolutions. Also you may want to try the ShiftedKerrSchild > > thorn (in the ETK), which enables a radial offset that shrinks the BH > > coordinate size but at the same time kills off enormous constraint > > violations near r=0. Unlike the existing KerrSchild thorn(s), this > > one uses the standard Kerr-Schild metric written in spherical > > coordinates and does the basis xform. > Right, I had completely forgotten about that one. Thank you. So > ShifterKerrSchild is actually different from Exact with its > Kerr_KerrSchild__epsilon parameter (ie it would do proper coordinate > transformation r -> r+r0 rather than just add r0 in some of the 1/r > terms)? >
KerrSchild_radial_shift sets r0. For more documentation, my Master's student George Vopal developed as part of his Master's research project a couple of interactive NRPy+ tutorial modules on the shifted Kerr-Schild solution (even confirming constraint convergence to zero in a standalone code): Basic equations (takes a minute to load): https://mybinder.org/v2/gh/zachetienne/nrpytutorial/master?filepath=Tutorial-ADM_Initial_Data-ShiftedKerrSchild.ipynb Numerical validation (takes a minute to load): https://mybinder.org/v2/gh/zachetienne/nrpytutorial/master?filepath=Tutorial-Start_to_Finish-BSSNCurvilinear-Setting_up_Shifted_KerrSchild_initial_data.ipynb > > Note that the goal is use it only as ID and not to reset the metric at > each time so I will have to modify ShifterKerrSchild a bit. > Should be a pretty simple change. > > Yours, > Roland > > -- > My email is as private as my paper mail. I therefore support encrypting > and signing email messages. Get my PGP key from http://pgp.mit.edu . >
_______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
