We perform statistical analyses of the infall of dark-matter onto clusters in numerical simulations within the concordance { \Lambda } CDM model .
By studying the infall profile around clusters of different mass , we find a linear relation between the mass and maximum infall velocities which reach \sim 900 km/s for the most massive groups .
The maximum infall velocity and the group mass follow a suitable power law fit of the form , V _ { inf } ^ { max } = ( M / m _ { 0 } ) ^ { \gamma } .
By comparing the measured infall velocity to the linear infall model with an exponential cutoff introduced by Croft et al. , we find that the best agreement is obtained for a critical overdensity \delta _ { c } = 45 .
We study the dependence of the direction of infall with respect to the cluster centres , and find that in the case of massive groups , the maximum alignment occurs at scales r \sim 6 h ^ { -1 } Mpc .
We obtain a logarithmic power-law relation between the average infall angle and the group mass .
We also study the dependence of the results on the local dark-matter density , finding a remarkable difference in the dynamical behaviour of low- and high-density particles .