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Dennis B Bowen

Publications and source records attributed to Dennis B Bowen.

PatchworkWave: A Multipatch Infrastructure for Multiphysics/Multiscale/Multiframe/Multimethod Simulations at Arbitrary Order

We present an extension of the PatchworkMHD code [1], itself an MHD-capable extension of thePatch-workcode [2], for which several algorithms presented here were co-developed. Its purpose is to create a“multipatch” scheme compatible with numerical simulations of arbitrary equations of motion at any dis-cretization order in space and time. In thePatchworkframework, the global simulation is comprised of anarbitrary number of moving, local meshes, or “patches”, which are free to employ their own resolution, co-ordinate system/topology, physics equations, reference frame, and in our new approach, numerical method.Each local patch exchanges boundary data with a single global patch on which all other patches residethrough a client-router-server parallelization model. In generalizingPatchworkto be compatible witharbitrary order time integration,PatchworkMHDandPatchworkWavehave significantly improved theinterpatch interpolation accuracy by removing an interpolation of interpolated data feedback present in theoriginalPatchworkcode. Furthermore, we extendPatchworkto bemultimethodby allowing multiplestate vectors to be updated simultaneously, with each state vector providing its own interpatch interpolationand transformation procedures. As such, our scheme is compatible with nearly any set of hyperbolic partialdifferential equations. We demonstrate our changes through the implementation of a scalar wave toy-modelthat is evolved on arbitrary, time dependent patch configurations at 4th order accuracy.

Dennis B Bowen

Circumbinary Disk Accretion into Spinning Black Hole Binaries

Supermassive black hole binaries are likely to accrete interstellar gas through a circumbinary disk.Shortly before merger, the inner portions of this circumbinary disk are subject to general relativisticeffects. To study this regime, we approximate the spacetime metric of close orbiting black holes bysuperimposing two boosted Kerr-Schild terms. After demonstrating the quality of this approximation,we carry out very long-term general relativistic magnetohydrodynamic simulations of the circumbinarydisk. We consider black holes with spin dimensionless parameters of magnitude 0.9, in one simula-tion parallel to the orbital angular momentum of the binary, but in another anti-parallel. These arecontrasted with spinless simulations. We find that, for a fixed surface mass density in the inner cir-cumbinary disk, aligned spins of this magnitude approximately reduce the mass accretion rate by 14%and counter-aligned spins increase it by 45%, leaving many other disk properties unchanged.

Federico G Lopez Armengol