Seminar 3-S2, Tuesday 19 October 2021, 14:00 (London Time)
Speaker: Richard Porter (School of Mathematics, University of Bristol, UK)
Title: Manipulating water waves using bathymetric plate arrays
Abstract: This talk will describe how closely-spaced arrays of vertical plates protruding from the bed of an incompressible fluid can be used to produce interesting effects on water waves propagating on the surface of the fluid. We will consider how both fully depth dependent and depth-averaged (shallow water) models are formulated and how they compare and illustrate their use in a number of different settings. For instance, we can generate examples of bathymetric devices which represent all-frequency all-angle refractive devices which allow negative refraction and for which the phase velocity is directed towards the source. Other examples include the use of bathymetric plate arrays to perfectly transmit energy through bends in waveguides and, when formed into a cylinder, act as a bathymetric lens.
Biography: Richard Porter has worked at the University of Bristol for over 25 years, first as a Research Assistant before becoming a lecturer in Applied Mathematics. His research interests mainly focus on the interaction of water waves with marine structures and developing mathematical tools for approximating solutions to the boundary-value problems that arise. The principle topics of interest include trapped and near-trapped waves, the design and modelling of ocean wave energy converters, the influence of floating ice and cracks in ice sheets on wave propagation and, more recently, metamaterials and their application in water wave settings.
He has published six papers with his father, been known to cycle to overseas conferences, and appeared in a BBC documentary which he has never watched.
Seminar 4-S2, Tuesday 26 October 2021, 14:00 (London Time)
Speaker: Alexei Maznev (Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139, USA)
Title: Self-collimation, Veselago lens, Dirac cones and embedded states in continuum in acoustics without phononic crystals and metamaterials
Self-collimation a.k.a. phonon focusing of surface acoustic waves on Ge (111)
Abstract: The concepts of photonic crystals and metamaterials initially appeared in optics and electromagnetism, and were subsequently extended to acoustic waves. However, a number of phenomena thought to be specific to these “artificial” media have been observed in solid state acoustics with conventional materials – in some cases well before the advent of metamaterials and photonic/phononic crystals. In this talk, which will cover both historical and recent research, we will discuss several such phenomena: (i) “self-collimation” of bulk and surface acoustic waves in natural crystals; (ii) negative group velocity, Veselago lens and Dirac cones exhibited by guided acoustic waves in plates; (iii) robust embedded states in continuum on natural crystal surfaces and in simple layered structures.
Biography: Alex Maznev received Diploma in physics from the Moscow Institute of Physics and Technology and PhD from the General Physics Institute of the Russian Academy of Sciences (thesis on laser-generated SAWs including the first experimental observation of surface phonon focusing). He held postdoctoral positions at the Freie Universität Berlin, as an Alexander von Humboldt Fellow, and at MIT, where he developed an optical heterodyning scheme for laser-induced transient grating experiment currently used in many labs. Subsequently, he worked as an industrial researcher (mainly at Philips Electronics North America) developing metrology systems for semiconductor industry using optical and optoacoustic techniques, before returning to MIT as a staff scientist. His current interests involve a broad range of topics pertaining to wave propagation phenomena, primarily in acoustics and related fields such as phonon-mediated heat transport on micro/nanoscale. He is collaborating with many groups around the world and has held visiting positions at Université du Maine in France, Hokkaido University in Japan, University of Witwatersrand in South Africa, and Universität Heidelberg in Germany.
Seminar 6-S2, Tuesday 09 November 2021, 14:00 (London Time)
Speaker: Gianluca Memoli (School of Engineering and Informatics, University of Sussex)
Seminar -S2, Tuesday 14 December 2021, 14:00 (London Time)
Speaker: Mordechai Segev (Solid State Institute and Physics Department, Technion – Israel Institute of Technology)