Investigation of Droplet Motion and Grouping

• Applicant: Professor Dr.-Ing. Bernhard Weigand
• Subject Area: Fluid Mechanics
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409029509

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.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicants: Professor Dr. Jerrold Barry Greenberg; Professor Dr. David Katoshevski