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Simulating the boundary layer between a white dwarf and its accretion disc

We describe the results of numerical simulations of the dynamics of the boundary layer (BL) between the accretion disk and the surface of a non-magnetic white dwarf (WD) for different viscosities which corresponds to different stages for dwarf novae burst cycles. The simulations cover the inner part of the accretion disk, the BL, and the upper atmosphere of the star. The high viscosity case, which corresponds to a dwarf nova in outburst, shows a optically thick BL which after one Keplerian rotation period (t_K=19s) extends more than 30 degrees to either side of the disk plane. The BL is optically thick and thus occludes part of the star. The low viscosity case, which corresponds to a dwarf nova in quiescense, also shows a BL, but it is optically thin.