Dynamical models of polar rings

A three-dimensional, first-order accurate, explicit, Eulerian, hydrodynamical computer code is used to study the dynamics of disks at various inclinations from the symmetry plane of an external, spheroidal potential and the evolution of polar rings. Inflow of matter is observed for highly inclined rings, but polar rings do not collapse toward the center of the potential. Old polar rings lose their inner regions due to differential precession as they try to settle toward the symmetry plane of the potential. At high inclinations, polar rings are transient but can survive for almost a Hubble time. The Papaloizou-Pringle instability appears in the evolution of the models. 5 refs