Logarithm of the number density is shown for different times for the case of preexisting clumps (RUN 2). The times are (a) 0, (b) 536, (c) 910, and (d) 1852 yr after the beginning of the fast wind. In the lower left panel we have labeled relevant areas of the interaction between the stellar wind and the ambient medium. The evolution of three clumps of different densities that start close to each other (labels 1–3) are also indicated for all times shown.