Vortex Rings and Jets ― Recent Developments in Near-field Dynamics

In this book, recent developments in our understanding of fundamental vortex ring and jet dynamics will be discussed, with a view to shed light upon their near-field behaviour which underpins much of their far-field characteristics. The chapters provide up-to-date research findings by their respective experts and seek to link near-field flow physics of vortex ring and jet flows with end-applications in mind. Over the past decade, our knowledge on vortex ring and jet flows has grown by leaps and bounds, thanks to increasing use of high-fidelity, high-accuracy experimental techniques and numerical simulations. As such, we now have a much better appreciation and understanding on the initiation and near-field developments of vortex ring and jet flows under many varied initial and boundary conditions. Chapter 1 outlines the vortex ring pinch-off phenomenon and how it relates to the initial stages of jet formations and subsequent jet behaviour, while Chapter 2 takes a closer look at the behaviour resulting from vortex ring impingement upon solid boundaries and how the use of a porous surface alters the impingement process. Chapters 3 and 4 focus upon the formation of synthetic jets from vortex ring structures experimentally and numerically, the challenges in understanding the relationships between their generation parameters and how they can be utilized in flow separation control problems. Chapter 5 looks at the use of imposing selected nozzle trailing-edge modifications to effect changes upon the near-field dynamics associated with circular, noncircular and coaxial jets, with a view to control their mixing behaviour. And last but not least, Chapter 6 details the use of unique impinging jet configurations and how they may lend themselves towards greater understanding and operating efficacies in heat transfer problems. This book will be useful to postgraduate students and researchers alike who wish to get up to speed regarding the latest developments in vortex ring and jet flow behaviour and how their interesting flow dynamics may be put into good use in their intended applications.

Dr. Simon C. M. YU
BEng(Hons) ACGI PhD DIC CEng FIMechE
Associate Professor and Head, Division of Aerospace Engineering

Dr. Yu obtained his BEng(Hons) ACGI and PhD DIC (under the late Prof. J. H. Whitelaw FRS) from the Department of Mechanical Engineering, Imperial College, London in 1987 and 1991 respectively. He joined the School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore in November 1991 as lecturer. He has published more than 100 referred journal papers in different areas of fluid mechanics and had held several administrative appointments at the university; Principal Staff Officer (President Office), University Council Member, Vice-Dean (Office of Admissions). He is currently Head of the Aerospace Engineering Division. He was appointed as the trainer for the Holistic Gas Turbine for Rolls Royce Aeroengine Singapore in 2009. He has been a Chartered Mechanical Engineer (CEng) since 1997 and was elected as Fellow of The Institution of Mechanical Engineers (FIMechE) U.K. in 2008.

TH New obtained his B.Eng (Hons) and PhD degrees from the National University of Singapore in 1998 and 2004 respectively. Between 2001 and 2005, he was with Temasek Laboratories at the National University of Singapore, where he investigated flow control problems such as jet-mixing enhancement and control strategies, drag reduction and ogive cylinder flows. It was then that he developed an interest in geometrically modified jet nozzles. From 2005 to 2010, he joined the University of Liverpool, United Kingdom, where he investigated the flow physics of single and coaxial nozzle jet flows with trailing-edge modifications. For his research in jet control techniques, he was awarded competitive research grants from the UK Engineering and Physical Science Research Council and The Royal Society. He returned to Singapore to join the Division of Aerospace Engineering, Nanyang Technological University in 2010. He has since being awarded several research grants in the areas of UAV aerodynamics, particle-laden flows and jet control. His active role in fluid-related research has seen key journal papers published in Journal of Fluid Mechanics; Physics of Fluids; Experiments in Fluids and AIAA Journal, as well as serving as a regular reviewer for these research journals. His current research interests include jet-in-crossflows, geometrically modified nozzles, jet vortex dynamics and UAV aerodynamics.