Day 1 :
University of Birmingham, UK
Time : 10:25-11:05
Hassan Hemida is a senior Lecturer and the Head of Research at the School of Civil Engineering, University of Birmingham. He is also the Director of the MRes in Railway System and Integration. He has a PhD in the field of crosswind flow around ground vehicles and his research interests range from fundamental thermo-fluids and CFD (LES, and, DES) to applied computational wind engineering. He has more than fifteen years of working experience in both academia and industry running research projects that involve steady and unsteady simulations of single and multiphase flows, with special emphases on wind engineering and train aerodynamics.
Traditionally, train aerodynamics was limited to the study of train drag reduction. Recently with the introduction of high-speed trains, the field of train aerodynamics became more and more important and of a direct concern to both train operators and manufacturers and new areas of research have been emerging. These include safety of trains in strong crosswinds, slipstream, noise and vibration, pressure pulses in tunnels and many other issues. Due to its own complexity and expenses, the measurements of aerodynamic phenomena on a full-scale train at the operating speed is extremely difficult and thus most of the researches of the aerodynamics of high-speed trains rely on small-scale physical modelling and computational fluid dynamics (CFD) techniques. Each of these has its own issues, however. The use of Computational Fluid Dynamics (CFD) to study train aerodynamics is an ever changing field due to continual increase in computational power. As new approaches become more viable, research must be conducted upon their validity. In this talk, the recent development of the use of CFD in train aerodynamics will be presented, starting from the drag reduction, crosswind forces on trains, slipstream and train pressure pulses on tunnels. Part of this talk will be also looking at the different CFD techniques and their validity for train aerodynamics and how they compare with model and full scale experiments.
Polytechnic University of Catalonia, Spain
Time : 10:25-11:05
Josep M Bergadà studied Mechanical Engineering at ETSEIAT (Escola Tècnica Superior d'Enginyeries Industrial i Aeronàutica de Terrassa)-UPC in 1990. He also did his PhD in Mechanical Engineering, Fluid Power Systems, at the same institution in 1996. During the period 2000 to 2010, he closely worked in the fluid power field with Prof. J Watton at Cardiff University, UK. His research focused on low Reynolds fluid mechanics applied to piston pumps and conical seat relief valves. During the period 2010-2014, his research was mostly based on collaboration with TU-Berlin, and focused on active flow control, studding the different fluidic oscillators and their possible applications. At present, active flow control applications as well as fluidic oscillator performance are his main research interests. He has over 50 international conference publications and journal papers, as well as several books on Fluid Mechanics and Fluid Power. He is currently an Editorial Board Member of an SCI journal.
It is well known that modifying the boundary layer separation point involves the modification of the forces acting onto a given bluff body. Traditionally, the separation point was usually delayed using passive flow control devices. Cars, trucks and aeroplanes have many of these devices. Quite recently, it was realized that the use of active flow control devices was producing very similar effects, having the capability of being switched on and off at users will and therefore implementing a new degree of freedom in the system where they are inserted. Regarding active flow control (AFC) devices, there are many possible configurations. AFC can be implemented using steady blowing or sucking, yet many researchers have observed that periodic forcing interacts more deeply with the boundary layer, therefore producing a huge modification to it and to the flow main parameters. When considering periodic forcing, it is relevant to evaluate the different fluidic oscillators, among them, the synthetic jets and fluidic actuators are the ones being more extensively used. During the presentation, some novel characteristics on fluidic actuators will be presented. Once the forcing device is chosen, the next step is to determine the location or locations the grooves need to be inserted. Groove location depends on the forcing system employed, forcing frequency as well as the momentum coefficient associated to the jet. At this point of the speech, some examples will be provided clarifying the effect onto the boundary layer and the downstream vortex shedding of several (AFC) devices. For some given applications, the optimum parameters regarding groove location, width, velocity ratio, etc., will be stablished. The speech will finish giving a list of possible future applications of (AFC).