  Using cosmological $N$-body simulations of dark matter haloes, we study the
effects of non-sphericity, substructure and streaming motions in reproducing
the structure and internal kinematics of clusters of galaxies from kinematical
measurements. Fitting an NFW model to the 3D density profile, we determine the
virial mass, concentration parameter and velocity anisotropy of the haloes, and
then calculate the profiles of projected velocity moments, as they would be
measured by a distant observer. Using these mock data, we apply a Jeans
analysis for spherical objects to reproduce the line-of-sight velocity
dispersion and kurtosis and fit the three parameters. We find that the
line-of-sight velocity dispersion and kurtosis profiles of a given halo can
vary considerably with the angle of view of the observer. We show that the
virial mass, concentration parameter and velocity anisotropy of the haloes can
be reproduced satisfactorily independently of the halo shape, although the
virial mass tends to be underestimated, the concentration parameter
overestimated, while the recovered anisotropy is typically more tangential than
the true one. The mass, concentration and velocity anisotropy of haloes are
recovered with better precision when their mean velocity profiles are near
zero.
