Formation of Accretion Disks
Accretion does not always form a
disk around the second star. For example, we saw in the case of Algol that there is evidence
for a small accretion stream that goes directly into the body of the second star rather than into
an orbiting disk.
However, in most cases it is expected that the dynamics associated with angular momentum
favor the
formation of an accretion disk.
Here are some
supercomputer
simulations
of accretion in binary stars (click on the first image displayed to start).