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The subproject A02 addresses drop and spray – wall film interactions whereby the drop liquid and the wall film liquid are different. Those interactions are relevant for numerous technical applications such as internal combustion engines as well as exhaust gas after-treatment systems. The impact of a drop on a wall film can result in generation of secondary droplets, which may contain both wall and drop liquid and can thus influence the combustion process. In case of exhaust gas after-treatment systems (i.e SCR deNOx) drop impingement of urea-water solution on the wall leads to heat transport processes, which in combination with the fluid transport due to drop impact have an influence on the decomposition of urea and thus the NOx Emissions. Current research focuses mainly on drop impact of dry substrates or on films of the same liquid. There are studies concerning drop impact on wall films of different liquids describing the drop impact phenomenologically but the underlying physics are still not fully understood. Specifically a model that covers the physical processes during the drop impact including the heat transport and characterization of secondary droplets is missing.

The Subproject A02 is part of the Collaborative Research Center SFB/TRR 150 where numerous experimental and numerical projects are coordinated to investigate the phenomena surrounding turbulent, chemically reactive, multiphase flows near walls.

At the Institute of Fluid Mechanics and Aerodynamics (SLA), the focus within the project is on single droplet experiments, which serve as a basis for analytical modelling and for the validation of numerical models. In addition to confocal chromatic sensor technology for precise measurement of the film thickness, the project also has a colour-sensitive high-speed camera at its disposal, which makes it possible to investigate multi-component drop impact of differently coloured liquids.