Astron. Astrophys. 337, 311-320 (1998)

Numerical computation of two dimensional wind accretion of isothermal gas

Eiji Shima ¹, Takuya Matsuda ², Ulrich Anzer ³, Gerhard Börner ³ and Henri M.J. Boffin <sup>4

1</sup> Kawasaki Heavy Industries, Kakamigahara, Gifu, Japan
² Department of Earth and Planetary Science, Kobe University, Kobe 657, Japan
³ Max-Planck Institut für Astrophysik, Postfach 1523, D-85740 Garching, Germany
⁴ Department of Physics and Astronomy, University of Wales, Cardiff CF2 3YB, UK

Received 21 April 1998 / Accepted 22 June 1998

Abstract

A new numerical algorithm for calculating isothermal wind accretion flows has been developed and is applied here to the analysis of the hydrodynamics of two-dimensional plane symmetric accretion flows in wind-fed sources. Polar coordinates are used to ensure fine resolution near the object. It is found that a thin accretion column is formed which shows wave-like oscillations. Small accretion disks are formed temporarily around the object. Mass accretion rate and angular momentum accretion rate exhibit quasi-periodic oscillations. The amplitudes of the oscillations depend on the size of the inner boundary, the number of grid points and the method of calculation. For a smaller size of the inner boundary, finer grids and more accurate numerical schemes, the amplitudes of the oscillation become larger.

Key words: accretion, accretion disks hydrodynamics instabilities shock waves methods: laboratory stars: pulsars: general

Send offprint requests to: U. Anzer

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Governing equations and numerical procedure
  • 2.1. Governing equations
  • 2.2. Initial and boundary conditions
  • 2.3. Computational mesh
  • 2.4. Finite volume method
  • 2.5. Simplified flux splitting (SFS) for isothermal gas
  • 2.6. Angular momentum conserving scheme
  • 2.7. Accurate local time stepping
  • 2.8. Units
• 3. Numerical results
  • 3.1. Calculated cases
  • 3.2. Mesh dependency of the LMC and AMC schemes
  • 3.3. Occurrence of oscillations and formation of accretion disks
  • 3.4. History of mass accretion rate and angular momentum accretion
    • 3.4.1. Effects of R_min and mesh size
    • 3.4.2. Effects of the Mach number
• 4. Summary and discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998
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