John F. Hawley

New paradigms for black hole accretion from high resolution supercomputer experiments

From a series of high resolution supercomputer calculations, new paradigms emerge for black hole accretion with angular momentum. We have discovered that the centrifugal barrier, or funnel wall, plays a key role in shock heating the inflowing supersonic fluid, producing a stationary thick disk with bipolar outflow. The infall dynamics are calculated in detail and followed until a steady state is reached. We delineate a number of distinct regimes of steady state flow in the two parameter solution space defined by the fluid’s angular momentum and the disk thickness. The essential physics is highlighted with selected numerical examples. The same code can calculate general relativistic magnetohydrodynamical flows near black holes.

Hollow conical jet models for SS 433 - A paradigm lost?

A precessing jet such as that in SS 433 may be approximated as an axisymmetric flow, if the precession time is short by comparison to the propagation time. A series of simulations has been conducted for precessing jets using an axisymmetric finite-difference hydrodynamics code. Examinations are made of hollow cylindrical jets, which lack the complication of a growing interior volume, and conical jets, which model the behavior of a precessing jet propagating on the surface of its precession cone. 25 refs.

Numerical simulations of AGNs

Abstract The role that numerical simulations play in the study of active galactic nuclei is reviewed. Some of the advantages and limitations of numerical work are discussed and illustrated with applications from jet and disk studies.