  We investigate the dynamics of spin-nonequilibrium electron systems for the
case when normal electron collisions prevail over the other scattering
processes and the "hydrodynamic flow" regime is realized. The hydrodynamic
equations for the electron liquid have been obtained and analyzed. We
demonstrate that oscillations of the spin polarization are possible in a
conducting ring with inhomogeneous magnetic properties. These low-decay
oscillations are accompanied by the oscillations of the drift current in the
ring. We demonstrate also that the spin polarization of the electron density
may be revealed via the voltage between the ends of the open circuit with an
inhomogeneous spin polarization. The effect may be observed both in the
hydrodynamic and diffusive regimes.
