Plenary Speakers

Presentation Title

Binary collisions of liquid droplets in a gaseous environment have been analysed experimentally for several decades, mainly aiming at deriving appropriate collision maps characterising the outcome of a the collision processs in termas of the non-dimensional impact parameter (i.e. lateral displacement of droplets centres upon contact) and the Weber-number (i.e. determined by the relative velocity and the diameter of the smaller droplet). This information is essential in modelling droplet collisions in the frame of a Euler/Lagrange calculation as commonly used for spraying systems in many engineering fields. Unfortunately such collision maps depend on a number of other parameters not involved in the two parameters impact parameter and Weber-number. These are mainly size ratio, viscosity ratio and properties of the gaseous environment. Therefore, a development of more generalised models (Sommerfeld 2016) including theoretically derived boundary lines require further detailed experiments for a range of liquid properties.

The present experimental studies were done using two vibrating orifice droplet generators (droplet size between 300 and 800 μm) and a backlight illumination combined with two high-speed cameras (Kuschel & Sommerfeld 2013; Sommerfeld & Kuschel 2016). Measurements for visualising the entire collision process were done with a lense yielding a resolution on 25 μm/pixel, in order to determine the collision outcome and to obtain the number and size of possible satellite droplets. The emphasis in these studies was the modification of the collision maps for a range of liquid viscosities between 1 mPa⋅s and 60 mPa⋅s (Figure 1 a) and different droplet size ratio, however concentrating first on identical viscosity. High resolution imaging was performed using between 2 and 5 μm/pixel. In these studies, details of the collision process were resolved, such as the occurrence of air cushions between the interacting liquids (Figure 1 b). Moreover, the collision behaviour of droplets with different viscous liquids was of interest (Figure 1c), a situation found in many applications. For this purpose, backlightning and a laser light sheet were used and one liquid was doped with fluorescent dye.

Martin Sommerfeld (Prof. Dr.-Ing) studied aeronautical engineering at the Technical University Aachen and received his Diploma in 1981. He completed his Doctoral degree (shock wave propagation through gas-particle mixtures) at the same University in 1984. Then he spent one year at Kyoto University Japan on a research fellowship. In 1986 he moved to the Institute of Fluid Mechanics (Prof. Durst, University Erlangen), headed the Two-Phase Flow research group and completed a Habilitation “Modelling and Calculation of Particle-Laden Flows using the Euler/Lagrange Approach”. In October 1994 he was appointed Professor of Mechanical Process Engineering (University Halle, Germany). In 1997 he received the DECHEMA Award for contributions to multiphase flow measurements, modelling and numerical prediction. From January 2017 his research group based in Halle (Saale) belongs to the Otto-von-Guericke University Magdeburg.

Martin Sommerfeld organised a continuing series of workshops on two-phase flow predictions, ASME symposia, the Int. Conf. on Multiphase Flow (ICMF 2007) and several other international conferences. He is chair of the ERCOFTAC special interest groups “dispersed two-phase flows” and “Oil & Gas” and the ProcessNet special topic group “computational fluid dynamics”. He has written 180 reviewed journal papers, 200 conference papers and several books and monographs, among that the book “Multiphase Flows with Droplets and Particles”. (2nd Edition, Crowe et al. 2012) and the ERCOFTAC Best Practice Guidelines for Computational Fluid Dynamics of Dispersed Multiphase Flows.

His research activities are mainly concerned with fundamentals of dispersed multi-phase flows with the aim of developing physical models for describing relevant transport phenomena. For the analysis of multi-phase flow phenomena detailed experiments using modern optical instrumentation as well as direct numerical simulations by the Lattice-Bolzmann-Method are performed. The developed models are used in the frame of the Euler/Lagrange computational approach for allowing the prediction of industrial processes involving dispersed multi-phase flows.

T.S. (Tim) Zhao is currently the Cheong Ying Chan Professor of Engineering and Environment, the Chair Professor of Mechanical & Aerospace Engineering at HKUST, the Director of the HKUST Energy Institute, and a Senior Fellow of the HKUST Institute for Advanced Study. He is an elected Fellow of the American Society Mechanical Engineers (ASME), Fellow of the Royal Society of Chemistry (RSC), and a Highly Cited Researcher by Thomson Reuters (2014, 2015, 2016, 2017).

Professor Zhao combines his expertise in research and technological innovation with a commitment to creating clean energy production and storage devices for a sustainable future. He has made seminal contributions in the areas of fuel cells, advanced batteries, multi-scale multiphase heat and mass transport with electrochemical reactions, and computational modeling. In addition to 4 edited books, 9 book chapters and over 67 keynote lectures at international conferences, he has published 310 papers in various prestigious Journals. These papers have collectively received more than 12,000 citations and earned Prof Zhao an h-index of 59 (Web of Science). In recognition of his research achievements, Prof Zhao has in recent years received many awards, including the 2014 Distinguished Research Excellence Award (HKUST), two State Natural Science Awards, the Croucher Senior Fellowship award, the Overseas Distinguished Young Scholars Award (NSFC), and the Yangtze River Chair Professorship, among others.

In the international community, Prof Zhao serves as Editor-in-Chief of Applied Thermal Engineering, Executive Editor of Science Bulletin, and Editor of RSC’s Energy & Environmental Science. He has served as an editorial board member for Energy & Environmental Science, Journal of Power Sources, and other 10 prestigious international Journals.