  Three-dimensional hydrodynamic calculations are performed in order to
investigate mass transfer in a close binary system, in which one component
undergoes mass loss through a wind. The mass ratio is assumed to be unity. The
radius of the mass-losing star is taken to be about a quarter of the separation
between the two stars. Calculations are performed for gases with a ratio of
specific heats gamma=1.01 and 5/3. Mass loss is assumed to be thermally driven
so that the other parameter is the sound speed of the gas on the mass-losing
star. Here, we focus our attention on two features: flow patterns and mass
accretion ratio, which we define as the ratio of the mass accretion rate onto
the companion to the mass loss rate from the mass-losing primary star. We
characterize the flow by the mean normal velocity of wind on the critical Roche
surface of the mass-losing star, Vr. When Vr<0.4 A Omega, where A and Omega are
the separation between the two stars and the angular orbital frequency of the
binary, respectively, we obtain Roche-lobe over-flow (RLOF), while for Vr>0.7 A
Omega we observe wind accretion. We find very complex flow patterns in between
these two extreme cases. We derive an empirical formula of the mass accretion
ratio in the low and in the high velocity regime.
