This is an animation of a simulation from that paper. This corresponds to Run B in the paper. The animation displays images of the density of the nebula. The grid is expanding along with the nebula, so the grid size is gradually increasing (note that the increase is not linear in time). These simulations were carried out using the VH-1 code.

In brief the simulation shows a fast wind interacting with a dense slow wind, whose velocity is 10 km/s. the density in the ambient wind is a factor of 10 higher at the equator than the poles. The fast wind starts out at 25 km/s and increases to a maximum value of a 1000 km/s. Initially the nebula is in a momentum-conserving stage, and the inner and outer shocks are to be found very close to each other. Note the wrinkling of the shock due to the Non-linear thin shell instability. As the velocity increases the inner shock pulls back, a hot low density bubble forms and the nebula enters an energy-conserving phase. Rayleigh-Taylor filaments are seen at the edge of the hot bubble. This is due to the acceleration of the high density shell by the low-density bubble. Finally the nebula is seen to eneter a self-similar stage where the shape does not change with time.

Compare the above simulation to this one.

In this case a constant fast wind of velocity 1000 km/s runs into a constant slow wind of velocity 10 km/s. Due to the large fast wind velocity the radiative, momentum-conserving stage is completely bypassed. These simulations do not show as much structure as the ones with an evolving wind. Some rippling of the nebular walls is seen due to shearing instabilities.