Coalescence
of diwhirls
If the distance between two solitary vortex pairs, diwhirls, is sufficiently small (less than about five times the size of the gap in the Taylor column), they slowly drift towards each other and finally coalesce. Consecutive stages of it are presented in the snapshots showing the cross section of the gap in the plane of the column axis (Groisman and Steinberg, PRL 97). Laser sheet illumination and light reflecting Kalliroscope flakes were used. One can see that the "daughter" diwhirl has exactly the same profile as each of its "parents". The daughter diwhirl inherited the two vortices that used to be at the outer sides of the parent diwhirls, while those two which used to be at their inner sides just annihilated. The diwhirl interaction becomes stronger as they get closer, so that their drift toward each other is a self accelerating process. In order to show different stages of the coalescence better, the snapshots were taken with uneven time intervals.
If the distance between two solitary vortex pairs, diwhirls, is sufficiently small (less than about five times the size of the gap in the Taylor column), they slowly drift towards each other and finally coalesce. Consecutive stages of it are presented in the snapshots showing the cross section of the gap in the plane of the column axis (Groisman and Steinberg, PRL 97). Laser sheet illumination and light reflecting Kalliroscope flakes were used. One can see that the "daughter" diwhirl has exactly the same profile as each of its "parents". The daughter diwhirl inherited the two vortices that used to be at the outer sides of the parent diwhirls, while those two which used to be at their inner sides just annihilated. The diwhirl interaction becomes stronger as they get closer, so that their drift toward each other is a self accelerating process. In order to show different stages of the coalescence better, the snapshots were taken with uneven time intervals.