P. Godon, NON-REFLECTIVE BOUNDARY-CONDITIONS AND THE VISCOUS INSTABILITY IN ACCRETION DISCS, Monthly Notices of the Royal Astronomical Society, 282(4), 1996, pp. 1107-1113
A numerical investigation is carried out to analyse the effects of the
outer boundary conditions on the viscous instability of accretion dis
cs. A one-dimensional time-dependent calculation of geometrically thin
accretion discs is used. When the outer boundary is reflective, oscil
lations are trapped between the outer boundary and the outer edge of t
he inner evanescent region. When the outer boundary is nonreflective,
the oscillations decay on a viscous time-scale. An analytical treatmen
t of numerically non-reflective boundary conditions is carried out for
a polytropic flow and for a gas including radiation.