On dynamics of nonmagnetic accretion disks

Axisymmetric accretion disks in vicinity of a central compact body are studied. In the case of non-viscous disk it is proven that all solutions for the midplane circular velocity are unstable. Hence, the pure hydrodynamic turbulence in accretion disks is possible. It is disproved the well-known arguments that an inviscid accretion disk must be sub-Keplerian. It is also demonstrated that the regular asymptotic solutions, often used in astrophysics, can lead to erroneous conclusions. It is proven that a laminar viscous disk can be approximated with a great precision by the vortex motion. Assuming that a turbulent gas tends to flow with minimal losses, we have shown that a turbulent disk tends to be Keplerian.