Two-dimensional hydrodynamic simulation of an accretion flow with radiative cooling in a close binary system

Abstract

Two-dimensional numerical simulations of an accretion flow in a close binary system are performed by solving the Euler equations with radiative transfer. In the present study, the specific heat ratio is assumed to be constant while radiative cooling effect is included as a non-adiabatic process. The cooling effect of the disc is considered by discharging energy in the vertical directions from the top and bottom surfaces of the disc. We use the flux-limited diffusion approximation to calculate the radiative heat flux values. Our calculations show that a disc structure appears and the spiral shocks are formed on the disc. These features are similar to that observed in the case of an adiabatic gas with a lower specific heat ratio, $γ=1.01$. It is found that when radiative cooling effect is accounted for, the mass of the disc becomes larger than that assuming $γ=5/3$, and smaller than that assuming $γ=1.01$. It is concluded that employing an adiabatic gas with a lower specific heat ratio is almost a valid assumption for simulating accretion disc with radiative cooling effect.