In resent years, Vicsek model has attracted more and more attention and been
well developed. However, the in-depth analysis on the convergence time are
scarce thus far. In this paper, we study some certain factors that mainly
govern the convergence time of Vicsek model. By extensively numerical
simulations, we find the convergence time scales in a power law with $r^2\ln N$
in the noise-free case, where $r$ and $N$ are horizon radius and the number of
particles. Furthermore, to accelerate the convergence, we propose a new model
in which the speed of each particle is variable. The convergence time can be
remarkably shortened compared with the standard Vicsek model.Comment: 11 pages, 6 figure