Encounter frequency versus distance from the cluster centre, shown for the high-mass cluster (dashed line) and selected time steps for the low-mass cluster (coloured solid lines). The encounter flux at the centre of the cluster decreases with increasing age for the intermediate-mass cluster – colours are the same as in Fig. 2. The horizontal dash-dotted line illustrates for comparison the current encounter frequency of the Sun with Galactic field stars (Rickman et al. 2008).