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The time-dependence of non-planar accretion discs. (English) Zbl 0564.76054

The equations which describe the evolution of a viscous tilted accretion disc subject to external torques are derived. For this purpose, a full hydrodynamical treatment is used. The equations are linearized in terms of the small tilt angle of the disc. The equation of state for the disc is assumed to be barotropic. The authors show that the previous attemps for deriving these equations are inadequate due to the inconsistency of some of the assumptions made.
The viscous forces tend to flatten the disc, which will be smoothed on a time-scale faster than the usual viscous one. For a Keplerian disc, a simple diffusion equation governing the tilt angle is obtained, with the condition that the viscosity parameter to be greater than the opening angle of the disc.
Reviewer: V.Ureche

MSC:

76E20 Stability and instability of geophysical and astrophysical flows
76U05 General theory of rotating fluids
85A30 Hydrodynamic and hydromagnetic problems in astronomy and astrophysics
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