  We present a numerical scheme for the evolution of an accretion disc through
a dwarf nova outburst. We introduce a time-varying artificial viscosity into an
existing smoothed particle hydrodynamics code optimised for two and
three-dimensional simulations of accretion discs. The technique gives rise to
coherent outbursts and can easily be adapted to include a complete treatment of
thermodynamics. We apply a two-dimensional isothermal scheme to the system SS
Cygni and present a wide range of observationally testable results.
