Comparisons of 2D and 3D simulations of mass transfer in semi-detached binaries

We present the results of systematic comparisons of two- and three-dimensio nal computations of the flow patterns in semi-detached binary systems. The 2D and 3D solutions are qualitatively similar only when the adiabatic index is gamma similar to 1 (the nearly isotermal case). The three-dimensional s tructure of the flow radically changes for large gamma; in particular, star ting from some value of gamma, no accretion disk forms in the system. We al so discuss the formation of spiral shock waves. The extended shock waves st retching beyond the disk are not a consequence of tidal interactions and re sult instead from collisions of gaseous flows.