Celestial fluid mechanics: new perspectives on the hydrodynamics of astrophysical discs

Gordon Ogilvie (DAMTP/IAS)

Astrophysical discs often deviate from the circular, planar forms assumed in classical accretion-disc theory. Gravitational interaction with orbital companions can cause discs to become elliptical, warped and tidally deformed. In this talk I will discuss some physical consequences of these situations and introduce some novel theoretical methods for studying them. Generalizations of the shearing-box model, incorporating the oscillatory geometry experienced by orbiting fluid elements, reveal hydrodynamic turbulence that results from the destabilization of internal waves. Many aspects of warped discs can be alternatively be studied using a standard shearing box that undergoes modulated vertical oscillations. The nonlinear secular hydrodynamics of eccentric discs can be discussed in a Hamiltonian
framework that connects with methods of celestial mechanics. Finally, a new affine model of astrophysical discs augments the computationally convenient equations of 2D hydrodynamics with the additional degrees of freedom needed to describe several of these situations.

Thursday, 1 March 2018