Angular Momentum Transport in Particle and Fluid Disks
نویسنده
چکیده
We examine the angular momentum transport properties of disks composed of macroscopic particles whose velocity dispersions are externally enhanced (“stirred”). Our simple Boltzmann equation model serves as an analogy for unmagnetized fluid disks in which turbulence may be driven by thermal convection. We show that interparticle collisions in particle disks play the same role as fluctuating pressure forces and viscous dissipation in turbulent disks: both transfer energy in random motions associated with one direction to those associated with another, and convert kinetic energy into heat. The direction of angular momentum transport in both particle and fluid disks is determined by the direction of external stirring and by the properties of the collision term in the Boltzmann equation (or its analogue in the fluid problem). In particular, our model problem yields inward transport for vertically or radially stirred disks, provided collisions are suitably inelastic; the transport is outwards in the elastic limit. Numerical simulations of hydrodynamic turbulence driven by thermal convection find inward transport; this requires that fluctuating pressure forces do little to no work, and is analogous to an externally stirred particle disk in which collisions are highly inelastic.
منابع مشابه
Momentum Transport in Particle and Fluid Disks
We examine the angular momentum transport properties of disks composed of macroscopic particles whose velocity dispersions are externally enhanced (“stirred”). Our simple Boltzmann equation model serves as an analogy for unmagnetized fluid disks in which turbulence may be driven by thermal convection. We show that interparticle collisions in particle disks play the same role as fluctuating pres...
متن کاملAngular Momentum Transport in Simulations of Accretion Disks
In this paper we briefly discuss the ways in which angular momentum transport is included in simulations of non-self-gravitating accretion disks, concentrating on disks in close binaries. Numerical approaches fall in two basic categories; particle based Lagrangian schemes, and grid based Eulerian techniques. Underlying the choice of numerical technique are assumptions that are made about disk p...
متن کاملاثر باد چرخشی در قرصهای برافزایشی فوق بحرانی با اعمال فشار تابشی
We solved one-dimensional hydrodynamic (HD) equations of the slim disks in the presence of the wind and in cylindrical coordinates using self-similar solution. We considered power-law function of for mass loss rate due to wind. Then, we considered mass loss, angular-momentum loss and energy loss in equations. Then, we treated the influence of wind on the dynamics of the system. As an agreement ...
متن کاملAngular Momentum Transport in Low Mass Accretion Disks
We consider the transport of angular momentum in accretion disks that are low mass, in the sense that the gravitational forces produced by the material in these disks has a negligible effect on disk dynamics. There is no established consensus on how this transport takes place. We note that for phenomenological reasons the traditional α model is probably not a good description of real disks. Her...
متن کاملTurbulent Angular Momentum Transport in Weakly-ionized Accretion Disks
Accretion disks are ubiquitous in the universe. Although difficult to observe directly, their presence is often inferred from the unique signature they imprint on the spectra of the systems in which they are observed. In addition, many properties of accretion-disk systems that would be otherwise mysterious are easily accounted for by the presence of matter accreting (accumulating) onto a centra...
متن کامل