Simple model of violent relaxation of a spherical stellar system

A spherical system with arbitrary mean velocities in the radial and transverse directions, but with zero dispersion of radial velocities, is considered as a model describing the violent relaxation of star clusters and galaxies. The model allows to reduce the infinite chain of Jeans' equations of moments to just three hydrodynamic equations. The found system of equations is consistent with the law of conservation of energy and the virial equation. This part of the work is devoted to a general description of the model, then the calculation results will be presented.