Experimental Investigation of the Impact of Single Droplets of Non-Newtonian Fluid

Book excerpt: This study is devoted to the investigation of impact of a paint drop onto a thin liquid film. In particular the mechanism of bubble entrapment during drop impact will be studied. The study is motivated by the technology of spray coatings. The bubbles occasionally appearing in the coating layer are defects which can be avoided by addition of so called deaerators produced by Evonik. In order to improve the quality of the coating the mechanisms of drop impact and bubble entrapment have to be investigated in detail. The study will be performed in cooperation with Dr. Joachim Venzmer (Evonik Goldschmidt GmbH, Essen). In this project single paint drops will be generated by a drop-on-demand generator. Paint will be provided by Evonik. Drops will then impact onto a dry od wetted substrate. Drop impact and spreading will be observed using a high-speed video system. Special tasks of this project are: Literature survey/Defining experimental parameters/Modification of the existing experimental setup/Experiments with liquid mixtures of different rheological behavior impacting on solid and prewetted surfaces/Determining the velocity threshold at which bubbles appear.