Investigation of Droplet Motion and Grouping

喷雾在各种技术系统中都有使用。喷雾的使用范围从燃料的燃烧到表面的定向涂层。这些喷雾的效率取决于液滴的动态行为，包括形成液滴群的倾向。这种集团化趋势对整个喷雾的蒸发和运动行为有很大影响，例如对涂层过程中液滴的分布也有很大影响。液滴的分组对能源和运输系统、涂层或药物输送(例如在吸入系统中)都有影响。因此，更好地了解所发生的现象，能够控制群体形成过程，从而提高系统的效率，例如在排放控制、材料节约、表面质量或药物分配方面。从理论、数值和实验三个方面对所发生的具体现象进行了研究。分组的整个过程可以用三个连续的阶段来描述。首先，基团的形成开始，液滴开始相互接近，然后是实际的接近过程，最后是液滴的凝聚。基团的形成可以例如通过外部流场或通过液滴形成过程来启动。调查的目的之一是研究可能的基团形成过程，确定影响和启动形成过程的方法，从而具体促进或避免液滴的凝聚。在该项目的第一个资助期内，已经通过实验、数值和分析研究了一个和几个液滴流内的液滴接近过程。在我们正在申请的第二个资助期，研究范围将扩大到包括详细调查液滴形状、液滴振荡、声场效应和液滴蒸发对液滴运动和成团行为的影响。申请伙伴BGU、Technion和ITLR拥有不同的实验、数值和分析方法，这些方法结合在一起，可以详细研究液滴成团的所有关键子过程。一些方法重叠，从而允许直接比较和验证结果。与该项目的第一阶段一样，计划在合作伙伴之间进行非常密集的合作。

Sprays are used in a wide variety of technical systems. The use of sprays ranges from the combustion of fuels to the targeted coating of surfaces. The efficiency of these sprays is determined by the dynamic behavior of the droplets, which includes the tendency to form droplet groups. This grouping tendency has a significant effect on the evaporation and movement behavior of the entire spray, e.g. also on the distribution of the droplets during coating processes. The grouping of droplets has ramifications in energy and transport systems, in coating or in drug delivery (e.g. in inhalation systems). A better understanding of the phenomena that occur, thus, enables the group formation process to be controlled and thus to increase the efficiency of the systems, for example with regard to emission control, material savings, surface quality or drug distribution.This application for the second funding period continues the work done in the first funding period and expands on it. The individual detailed phenomena that occur are investigated theoretically, numerically and experimentally. The entire process of grouping can be described by three successive phases. First, the formation of groups is initiated and the droplets begin to approach each other, followed by the actual approach process, which finally ends with droplet coagulation. The formation of groups can be initiated, for example by the external flow field or by the droplet formation process. One aim of the investigations is to study possible processes of group formation, to identify methods for influencing and initializing the formation process and thus to specifically promote or avoid the coagulation of droplets. In the first funding period of the project, the approach processes of droplets within one and several droplet steams were already investigated experimentally, numerically and analytically. In the second funding period, which we are applying for, the investigations are to be extended to include a detailed investigation of the influences of droplet shape, droplet oscillations, the effect of an acoustic field and the drop evaporation on the droplet movement and the grouping behavior.The applying partners, BGU, Technion and ITLR, have different experimental, numerical and analytical methods at their disposal, which, when combined, allow to study all crucial sub-processes of droplet grouping in detail. Some methods overlap, thus allowing direct comparison and validation of the results. As in the first phase of the project, a very intensive cooperation between the partners is planned.