Experimental and computational investigation of droplet impingement at high Weber numbers on dry and wetted surfaces

• Applicant: Dr.-Ing. Stephan Bansmer
• Subject Area: Fluid Mechanics
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260485598

Within the proposed research project, the phenomenon of droplet impingement on dry and wetted surfaces at high Weber numbers shall be scientifically investigated with experimental and computational methods. Research on droplet impingement at high Weber numbers is a fundamental aspect in understanding and modelling many technical processes that involve multiphase flow, including road vehicle soiling and aircraft icing. Beyond understanding the physical process of droplet impingement, it is the goal to verify current impingement models (e.g. spreading, size of lamella, dynamic contact angles) for their validity at high Weber numbers, but also to measure the secondary droplets that are created during the splashing process. From an engineering perspective, these secondary droplets are shed back to the surrounding flow, and consequently only a fraction of the original droplet mass is remaining on the surface that influences the contamination process in the case of road vehicle soiling. As a particularly interesting result of the first funding period, an unexpected mechanism of secondary droplet formation was identified during impact studies on moving liquid films. In this case, the upper free rim of the lamella does not move backwards, as is usually the case with small Weber numbers. Instead, the lamella ruptures in its middle, sometimes even at the lower edge close to the solid wall, and finally atomizes completely in secondary drops. Parallel to this, many researchers have pointed out the significance of the gas phase during the drop impact. Against this background, many new and fundamental findings are to be expected. Cooperation with TU München and TU Darmstadt regarding computational and experimental analysis of the acquired data completes the proposed project.

• DFG Programme: Research Grants