[Users] BSSN, 8th order accurate -- how much dissipation?

[Erik Schnetter]

I am trying to set up a binary black hole simulation that uses 8th
order accurate finite differencing. (I need the black holes to be
highly resolved, and I don't need the wave zone, thus I am not use
AMR.) On the other hand, I am using Cartoon2D, and I extended it to
support 8th order interpolation.

My problem is that I cannot get the simulation started well. After a
few (about 70) time steps, the code aborts due to nans. Of course,
having modified thorn Cartoon2D, I cannot exclude that I made an error
there. On the other hand, I did find some pre-existing errors that I
corrected.

I wonder: What are good settings for numerical dissipation in this
case (ML_BSSN with fdOrder=8)? I see a sample parameter file that uses
epsDiss = 0.1; should I expect this to work? Would puncture initial
conditions need any kind of special treatment? (I'm using
TwoPunctures.)

Thanks,
-erik

-- 
Erik Schnetter <eschnetter at perimeterinstitute.ca>
http://www.perimeterinstitute.ca/personal/eschnetter/