Hydrodynamic model for a system of self-propelling particles with conservative kinematic constraints

We consider the dynamics of systems of self-propelling particles with kinematic constraints on the velocities. A continuum model for a discrete algorithm used in works by Vicsek et al. is proposed. For a case of planar geometry, finite-flocking behavior is obtained. The circulation of the velocity field is found not to be conserved. The stability of ordered motion with respect to noise is discussed.