Hydrodynamic Turbulence in Accretion Disks
Abstract
Turbulent viscosity in cold accretion disks is likely to be hydrodynamic in origin. We investigate the growth of hydrodynamic perturbations in a small region of a disk, which we model as a linear shear flow with Coriolis force, between two parallel walls. Although there are no exponentially growing eigenmodes in this system, because of the non-normal nature of the modes, it is possible to have a large transient growth in the energy of certain perturbations. For a constant angular momentum disk, the energy grows by more than a factor of 1000 for a Reynolds number of only 1000, and so turbulence is easily excited. For a Keplerian disk, the growth is more modest, and energy growth by a factor of 1000 requires a Reynolds number of nearly a million. Accretion disks have even larger Reynolds numbers than this. Therefore, transient growth of perturbations could seed turbulence in such disks.
Keywords
Cite
@article{arxiv.astro-ph/0501468,
title = {Hydrodynamic Turbulence in Accretion Disks},
author = {Banibrata Mukhopadhyay and Niayesh Afshordi and Ramesh Narayan},
journal= {arXiv preprint arXiv:astro-ph/0501468},
year = {2007}
}
Comments
6 pages including 5 figures. To appear in the proceedings of 22nd Texas Symposium on Relativistic Astrophysics, Stanford University, December 13-17, 2004