Liquid drops play a dominant role in numerous industrial applications, such as spray coating, spray painting, inkjet printing, lithography processes, and spraying/sprinkling in agriculture or gardening. In all of these examples, the generation, flight, impact, and spreading of drops are separate stages of the corresponding industrial processes, which are all thoroughly studied for many years. This thesis focuses on drop dynamics, impact phenomena, Leidenfrost drops, and pouring flows. Based on extensive analysis and numerical results, various mechanisms by which drops can deform are resolved in detail, in both fundamental and industrial contexts. The title of the thesis, Dynamics of Deforming Drops, can be explained in two ways. Drops can be deformed and moving drops can deform another liquid surface. Large part of the study focuses on the small scale deformations of the liquid surface(s) at the bottom of the impacting drop/object, induced by the force exerted by the gas that is squeezed out between the falling object and the bottom surface. This can result in small air bubble entrapment, which is generally undesired in applications. The results of interferometry experiments and Boundary Integral simulations show that there exists a maximal entrained bubble size for some impact velocity. The mechanism of small air bubble entrapment applies for impact of a liquid drop onto a solid surface, impact of a liquid drop onto a (deep) pool, and impact of a solid sphere onto a pool. Other covered subjects are the high-speed impact of a train of microdrops on a pool, instabilities at Leidenfrost drops, drop deformation induced by the impact of a picosecond laser-pulse, and pouring flows. The study of the response of drops impacted by a focused laser pulse is motivated by Extreme Ultraviolet (EUV) lithography, which is used for the creation of nanometer-sized patterns on electronic chips in, for example, mobile phones. To print the features at high resolution, one needs high energy radiation. In EUV-machines this radiation results from liquid tin sheets that are impacted by a laser-pulse, resulting in the formation of plasma. The fluid dynamics play a crucial role for improving the efficiency of the EUV machine.
|Award date||28 Aug 2015|
|Place of Publication||Enschede|
|Publication status||Published - 28 Aug 2015|