  We propose a new approach to study the dynamical implications of mass models
of clusters for the velocity structure of galaxies in the core. Strong and weak
lensing data are used to construct the total mass profile of the cluster, which
is used in conjunction with the optical galaxy data to solve in detail for the
nature of galaxy orbits and the velocity anisotropy in the central regions. We
also examine other observationally and physically motivated mass models,
specifically those obtained from X-ray observations and N-body simulations. The
aim of this analysis is to understand qualitatively the structure of the core
and test some of the key assumptions of the standard picture of cluster
formation regarding relaxation, virialization and equilibrium. This technique
is applied to the cluster Abell 2218, where we find evidence for an anisotropic
core, which we interpret to indicate the existence of a dynamically disturbed
central region. We find that the requirement of physically meaningful solutions
for the velocity anisotropy places stringent bounds on the slope of cluster
density profiles in the inner regions.
