Data analysis

Fig. 3.53 to Fig. 3.60 was a display which snapshot the density contour and clusters size distribution at 25ps, 50ps and 150ps from y-z plane of xenon droplet pair collision in head-on cases. At relative velocity 250m/s, the droplet distribution had no obvious changes after collision and only few pieces formed. Until the relative velocity reached 750m/s, while the droplets collided and the coalesced, the surface area tended to be larger and density of the area close to the droplet surface was smaller, but no more pieces formed nevertheless. When the relative velocity was 1250m/s to 1750m/s, the number of the pieces tended to increase as the velocity increases and we could apparently observe from the density contour at 75ps that the surface area of the

droplets increased and the density of the center of the droplets decreased after collision. But at 150ps, the droplet which stretched because of collision shrank to a smaller one and its density of the center increased also. When the relative velocity was 2000m/s, although a phenomenon like net occurred, the number of pieces increased substantially. But at 150ps, we could observe that the droplets coalesced gradually and some of the pieces became larger ones because of coalescence. When the relative velocity was 2250m/s, the pieces formed by the droplets after collision distributed evenly along the center of collision and the size of fragment was more average at 150ps than at 75ps. Fig. 3.61 to Fig. 3.63 was a display which snapshot the density contour and clusters size distribution at 25ps, 50ps and 150ps from y-z plane of helium droplet pair collision in head-on cases. At relative velocity 250m/s, although coalescence occurred, the helium droplet had more average density from the center to the surface in density contour at 150ps compared with the xenon droplet coalescence and also had larger entirely surface area, but fewer fragments formed. However, when the relative velocity was 500m/s and 750m/s, the surface area of droplet was apparently larger as relative velocity was higher at 75ps and fragments formed more easily. In Density contour at 150ps, we could observe that along the center of the droplet, the size of the fragments became smaller and the number of the fragments became larger while the radius of the droplets increased.

Fig. 3.64 to Fig. 3.75 were the data analysis of xenon droplet pair collision at relative velocity 250m/s, 500m/s , and 750m/s and impact parameter 0, 25nm, 50nm, and 75nm[Liu, et al., 1997 and marcus, et al., 1998]. Fig. 3.64 (a) was the atom

variation of the biggest fragment from droplet and through this figure we could find that the atom number was raise by the droplet coalescence. Fig. 3.64 (b) was the variation of temperature (K) and through it we could find that at 25ps, it was the collision between xenon atoms that made the temperature increase, but in 25ps to 100ps, it was coalescence that made the temperature descend substantially, however the evaporation made the temperature tend to be raise. Fig. 3.64 (c) was the rotation energy change of the biggest droplet as the time increased. And Fig. 3.64 (d) was the angular momentum distribution of different direction as the time increased. Compared Fig. 3.64 to Fig. 3.66, we could find out that as the velocity increased, the temperature was raised apparently at collision and both the rotation energy and angular momentum of every direction increased. Fig. 3.67 to Fig. 3.69 was the data analysis at impact parameter 25nm. Both of them were coalescence cases, therefore the atom number of the biggest droplet tended to decrease because of evaporation and the temperature increased as the relative velocity of collision increased. Moreover, on account of non-head cases, the rotation energy increased substantially after collision and the angular momentum of y-direction tended to be raise as the velocity increased.

Compared Fig. 3.70 to Fig. 3.75, we could find that the rotation energy and the angular momentum of y-direction also rose as the impact parameter increased. And Fig. 3.76 shown that at 275ps, the rotation energy descended on account of stretching separation and followed by the substantially decreasing of the angular momentum of y-direction. Fig 3.76 to Fig 3.87 shown the data analysis of helium droplet pair collision when the relative velocities were 250m/s, 500m/s, and 750m/s and the impact parameters were 0, 25nm,50nm, and 75nm. In head-on case, the variation tendency of

temperature, rotation energy and angular momentum result in coalescence were the same as the variation tendency of xenon droplet coalescence at relative velocity 250m/s. However, at 500m/s and 750m/s, shattering occurred result in the decrease of the atom number of the biggest droplet and the decrease of temperature, and that rotation energy and angular momentum had diversified variation result from the collision between the biggest droplet and other fragment. In non-head on cases, Fig.

3.79 and Fig. 3.82 had the same variation tendency as stretching coalescence cases of xenon droplet. Fig. 3.84 to Fig. 3.87 shown the stretching separation of droplets including the quickly decrease of temperature after the droplets separated, the decrease of rotation energy and the trend which the angular momentum became gentle on y-direction. On the contrary, in the other cases which result coalescence, when the impact parameter or relative velocity increased, the temperature, rotation energy and

angular momentum of collision all increase substantially.

Fig. 3.88 to Fig. 3.91 were the data analysis at the same relative velocity and impact parameter. According to Fig. 3.88 and Fig. 3.89, we could observe that in the same coalescence case, the helium droplet had the greatest number of atom, the faster decrease of rotation energy and the greatest angular momentum and in conclusion the variations tendency of helium droplet were generally similar. Fig. 3.90 shown that helium atom occurred shattering and then the rotation energy and angular momentum of it had substantially changes by the separation of the droplet. In Fig. 3.91, the helium droplets and xenon droplets were both had stretching separation, but the argon droplets had coalescence. We could clearly find that the separation time of xenon droplets was later than of helium droplet, decrease range of the rotation energy of xenon was not larger than of helium and the angular momentum of both xenon and helium became minimized after separation.