  Radiation-driven outflows play a crucial role in extracting mass and angular
momentum from binary systems undergoing rapid mass transfer at super-Eddington
rates. To study the mass transfer process from a massive donor star to a
stellar-mass black hole (BH), we perform multi-dimensional
radiation-hydrodynamical simulations that follow accretion flows from the first
Lagrange point down to about a hundred times the Schwarzschild radius of the
accreting BH. Our simulations reveal that rapid mass transfer occurring at over
a thousand times the Eddington rate leads to significant mass loss from the
accretion disk via radiation-driven outflows. Consequently, the inflow rates at
the innermost radius are regulated by two orders of magnitude smaller than the
transfer rates. We find that convective motions within the accretion disk drive
outward energy and momentum transport, enhancing the radiation pressure in the
outskirts of the disk and ultimately generating large-scale outflows with
sufficient energy to leave the binary. Furthermore, we observe strong
anisotropy in the outflows, which occur preferentially toward both the closest
and furthest points from the donor star. However, when averaged over all
directions, the specific angular momentum of the outflows is nearly comparable
to the value predicted in the isotropic emission case. Based on our simulation
results, we propose a formula that quantifies the mass growth rates on BHs and
the mass loss rates from binaries due to radiation-driven outflows. This
formula provides important implications for the binary evolution and the
formation of merging binary BHs.
