ILASS–Europe 2019, 29th Conference on Liquid Atomization and Spray Systems, 2-4 September 2019, Paris, France This work is licensed under a Creative Commons 4.0 International License (CC BY-NC-ND 4.0). The International Research Training Group "Droplet Interaction Technologies" (DROPIT): Selected Results G.E. Cossali 1 , B. Weigand* 2 , G. Lamanna 2 , S. Tonini 1 1 Dept. of Engineering and Applied Science, University of Bergamo, Italy 2 Institute of Aerospace Thermodynamics, University of Stuttgart, Germany *Corresponding author: Bernhard.Weigand@itlr.uni-stuttgart.de Abstract The International Research Training Group (IRTG) "Droplet Interaction Technologies" (GRK 2160/1) was established in October 2016 to focus on detailed droplet processes. Droplet interaction technologies have a large number of applications in a variety of technological processes, such as spray cooling, fuel injection, coating technologies or the generation of encapsulated materials in the pharmaceutical industry. A key feature of this large research project lies in the systematic study of the interdependencies between small- scale and large-scale dynamics through an integrated numerical, experimental and theoretical approach. The objective is to identify the mechanisms through which small-scale interactions at the interface can couple with and influence large scale features in the main flow. DROPIT is a joint initiative of the University of Stuttgart in Germany, the University of Bergamo and the University of Trento in Italy. The project consists of 17 subprojects, which are structured into three main research areas (drop- gas interaction, drop-wall interaction, drop-liquid interaction). It involves researchers from a large number of different disciplines like Mathematics, Environmental Engineering, Aerospace and Mechanical Engineering, Informatics and Computer Sciences. The project further consists of an extensive qualification program which aims at fostering the education of young scientists and providing them the knowledge and skills to conduct independent research. The paper gives an overview of the structure and the research activities within GRK 2160/1 as well as on the qualification program implemented. Selected scientific results, e.g. on multi-scale modelling of droplet dynamics in compressible flows, gas kinetic simulations of micro-drop-gas interactions, upscaling of coupled free-flow and porous-media flow processes, micro- and macro-drop impact dynamics with miscible fluids and novel optical techniques for micro-fluid dynamics are shown. The main purpose of the paper is to familiarize colleagues with this extensive research effort in the area of droplet interaction technologies and to exchange ideas and promote future collaboration with others in this field. Keywords: droplet dynamics, numerical methods, experiments, splashing, porous media Introduction Droplet interaction technologies find application in a large number of technological and industrial processes. These include spray cooling in the food and chemical industry, spray drying absorption for waste and pollutant treatment in process engineering, droplet collisions for the generation of powders and encapsulated material in the food and pharmaceutical industry, drop evaporation and droplet-wall interaction in internal combustion and aeronautical engines as well as in coating technologies. In all these applications, small scale fluid dynamics may have a huge impact on the large scale flow pattern, leading to drag reduction, heat transfer enhancement or depression, phase transition kinetics (e.g. drop condensation or nucleate boiling), acoustic impedance and optical reflection. To date the consequences of the presence of different length scales on macroscopic properties and the associated amplification of surface transport has remained largely unexplored, being limited mainly to the formulation of empirical correlations based solely on macroscopic observations. The novelty and uniqueness of the GRK 2160/1 lies in the fact that here a systematic study is undertaken to investigate the interdependencies between small-scale and large-scale dynamics in the field of droplet interaction technologies. Due to the complexity of the problem, the analysis of such micro/macro interactions is not limited to one single aspect. Rather, an integrated approach is chosen that evolves along three parallel pathways, namely a numerical, experimental and theoretical approach [1]. More detailed information concerning the International Research Training Group GRK 2160/1 can be found online: www.project.uni-stuttgart.de/dropit/. Structure of the International Research Training Group GRK2160/1 The International Research Training Group is structured into three main research areas (RA-A to RA-C), comprising 17 subprojects, listed below together with the responsible principle investigators: