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Aggregation, Collisions, and Breakup
Published in Efstathios E. Michaelides, Clayton T. Crowe, John D. Schwarzkopf, Multiphase Flow Handbook, 2016
Efstathios E. Michaelides, Clayton T. Crowe, John D. Schwarzkopf
crown-like sheet. A number of small jets then appear at the edge of this sheet, subsequently breaking up into secondary droplets. e drop can also break up during its receding phase. is receding breakup is caused by a disjoining of the contact line due to the local wall microstructure or chemical inhomogeneity. e partial rebound occurs when the duration of the central jet stretching is longer than the time required for its capillary breakup. Drop impact onto a highly hydrophobic surface can lead to the complete rebound. If the parameters of drop impact are below the splashing threshold, it deposits on the surface without breakup. An empirical relation for the splashing threshold was obtained by Mundo et al. (1998). It was assumed that drop will not splash if K = WeOh -0.4 657 (14.61)
Thermal transport during drop-on-drop impact on a heated superhydrophobic substrate
Published in Numerical Heat Transfer, Part B: Fundamentals, 2023
Ankush Kumar Jaiswal, Sameer Khandekar
Heat transfer during the drop-on-drop impact is highly dependent on the evolution of equivalent wetted area of droplets after merging. The area of wetting and spread diameter of drop-on-drop impact is dependent on the impact velocity, wettability of the substrate, and fluid properties. Furthermore, the temperature difference between the substrate and droplet also plays an important role in the amount of heat transfer from the heated wall. The temperature contour of axisymmetric domain during the drop-on-drop impact with WeDroplet #2 being 1.0 and 8.2 is shown in Figures 3a, b, respectively, reveals the mechanism of heat transfer. It can be observed that the trend of heat transfer with these two We numbers are significantly different. In both cases, there is formation of low-pressure neck region having negative curvature compared to the bulk of droplet. This pressure difference along with the momentum of Droplet #2 causes the rapid evolution in interfacial shape of the combined droplet mass. The mechanism of evolution of interface is discussed elsewhere [26]. Here, we focus only on the heat transfer during such impact.