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Formation, Breakup and Coalescence of Droplets

From rain drops landing on the ocean to inkjet printing, drop formation and impact are ubiquitous processes in both nature and industry. It is generally accepted that there is still much to understand about drop breakup and splashing and these topics have gained additional importance motivated by the enormous potential of inkjet, spray and coating technologies in 3D printing. In fact, most methods aiming to model and predict droplet behaviour are either inaccurate or unsuitable for industrial applications. Furthermore, theoretical models are extremely hard to validate, and therefore as a consequence industry relies on empirical trial and error testing when developing and optimizing droplet technologies.

In this talk I will give an overview of my studies that are aiming to bridge the existing gaps between applied and theoretical sciences, and also to an extent, those existing between academic and industrial work in the area of droplet science. The talk will focus on comparisons between experimental data and models and will highlight some interesting phenomena that have been shown recently to be arising in these topics. The first part of the talk will concentrate on the study of the breakup of liquid filaments and drop formation. My results will show that whether a thin filament has a tendency to break up or not into droplets will be dependent only on the liquid properties and the geometry of the system, and that this behaviour is universal. The second part of the talk will focus on the impact, coalescence, mixing and splashing of droplets. While the impact of droplets on to sessile solid substrates has been successfully studied in recent years, the impact on moving liquids has remained vastly unexplored due to practical difficulties. My talk will present the experimental arrangements that will overcome such limitations and will also investigate the impact of droplets on to diverse substrates including moving pools of the same liquid. My results will report the existence of distinct regimes of behaviour that are determined only by the initial dynamic conditions and the properties of the fluid. The third, and last part of my presentation, will conclude with some suggested directions for future work.

Biography

Dr. J.R. Castrejon-Pita is a Senior Research Associate and Fellow at the University of Cambridge. He was awarded his MSc in Fluid Mechanics from the National University of Mexico in 2003, and his PhD in Quantum Optics from Imperial College in 2007. He joined the Engineering Department at the University of Cambridge as a Research Assistant in 2006, and has held the following positions within Cambridge University: Research Associate (2007 to 2014), Senior Member of Wolfson College (2008 to 2013) and Senior Research Associate (2014-present). Additionally, he became the Isaac Newton Trust Fellow and a Governing Body Fellow of Wolfson College in 2013. He has carried out undergraduate teaching as a Senior Demonstrator in the Cavendish Laboratory since 2007, and as a Teaching Fellow in Mathematics in the Engineering Department since 2013.

His interests lie in the field of fluid mechanics, particularly in the understanding of fundamental processes during liquid breakup, coalescence and splashing. His projects have been funded both by research councils (EPSRC-UK) and industry. His industrial partners include Airbus, FujiFilm, Xaar plc and AkzoNobel. He has published a total of 37 papers in peer-reviewed journals, including several in Physical Review, and has refereed over 50 papers in journals such as the Journal of Fluid Mechanics, Biomicrofluidics, Physics of Fluids and Nature Communications. His collaborative network is extensive and includes Professors O. Basaran (Purdue University, US), J. Garcia-Garcia (Seville University, Spain), J. Hinch and J. Lister (Cambridge University).