  We present 3D hydrodynamical simulations of the separated binary RS Ophiuchi
(RS Oph), a recurrent nova and potential progenitor of a SN Ia. RS Oph is
composed of a red giant (RG) and a white dwarf (WD) whose mass is close to the
Chandrasekhar limit. In an isothermal scenario, the WD accrets about 10% of a
20 km/s RG wind by a non-Keplerian accretion disk with strong spiral shocks,
and about 2% of a 60 km/s RG wind by what we term a 'turbulent accretion ball'.
A significantly larger impact have the thermodynamics. In an adiabatic scenario
only about 0.7% of the 20 km/s RG wind is accreted. The rate of change of the
system separation due to mass and angular momentum loss out of the system is
negative in all three cases studied, but is ten times smaller for a fast RG
wind (60 km/s) than for a slow RG wind (20 km/s). The results demonstrate that
existing nova models and observed recurrence times fit well together with 3D
wind accretion and that RS Oph is one of the most promising systems to become
an SN Ia.
