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Numerical simulations have been conducted which explore the instability of gaseous jets such as those originating from active galactic nuclei. In order to achieve sufficient resolution in a jet to resolve the instabilities which cause its disruption, the simulations focus on a short segment of a jet, approximating the dynamics using periodic boundary conditions. Many Mach 2 and Mach 4, 2-dimensional simulations of periodic jets have been run on a Cray-2, CM-200 and CM-5 using the Piecewise-Parabolic-Method (PPM) with resolutions ranging from 40 to 700 computational zones across the width of the jet. The jets in the higher resolution simulations (those with a resolution of at least 150 zones across the jet width) are disrupted after nonlinear kink instabilities grow strong and disrupt the jet boundary, allowing filaments of denser external gas to enter the jet. These filaments of external gas absorb the kinetic energy of the jet as the momentum of the jet gas is transferred to them. The lower resolution in the simulations with less that 150 zones across the jet width inhibits the formation of filaments and delays the growth of the nonlinear kink instabilities. The absence of filaments for jet deceleration and the delayed growth of the kink instabilities cause the lower resolution simulations to produce different jet behaviour on both large and small scales.
Computing resources were provided by the Minnesota Supercomputer Institute and the Army High Performance Computing Research Center (which is supported though the Army Research Office and the University of Minnesota).
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