סמינר מחלקה של אוסמה קדרי - גלי כוח כבידה אקוסטיים - התמקדות באינטראקציה משולשת לא ליניארית
School of Mechanical Engineering Seminar
wednesday May 24.5.2023 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Acoustic-Gravity Waves – a focus on nonlinear triad interaction
Usama Kadri
senior lecturer, Cardiff University, UK
In linear water wave theory, acoustic (compression) waves are virtually decoupled from free-surface (gravity) waves, since the speed of sound in water far exceeds the maximum phase speed of gravity waves. Nevertheless, we argue theoretically that these two types of wave motion could exchange energy via nonlinear resonant triad interactions. There are two cases of interest this talk focuses on: (I) two gravity waves interacting with an acoustic mode of a comparable timescale; and (II) two acoustic modes interacting with a gravity wave of a comparable lengthscale. Using multiscale analysis cubic nonlinear Schrödinger-type evolution equations are derived. For finely tuned monochromatic waves almost all energy initially stored in the gravity waves transfers into the acoustic mode, whereas for wavepackets energy transfer becomes much less efficient.
Implications of the result are presented for a wide range of applications: from oceanic scale microseisms (faint earth tremors), wave energy harnessing and tsunami generation and mitigation, to lab-size time reversals, standing Faraday waves in an oscillating bath, and pilot-wave quantum analogues. The talk is concluded with a discussion over pushing the boundaries towards the derivation of general evolution equations.
Biography
I am an Aerospace Engineer, an Applied Mathematician, and a Science Communicator. My research focus lies in the area of fluid dynamics and nonlinear phenomena. Specifically, it is concerned with studying “acoustic–gravity waves”, which I employ to address most challenging questions with high impact on science and society. Recently I have focused on the early detection and mitigation of tsunami, in collaboration with the UNESCO; Covid-19; the missing Malaysian Airplane MH370; and Quantum Analogues. My approach is theoretical mathematical, combined with numerical modelling, lab experiments, and field-data analysis.
I obtained a B.Sc. and M.Sc. in Aerospace Engineering at the Technion, and a PhD in Applied Science at TU Delft (2009) under the supervision of Dist. Prof. and V. Rector R.F. Mudde, and Prof. R.V.A. Oliemans, where I also gave consultancy to oil & gas related industry (i.e., Shell, TNO), and spent some time at NTNU in Norway. I was a postdoc at CEE, Technion where I started working on acoustic-gravity waves with Prof. Micky Stiassnie (2010-2013), after which I was a Visiting Scholar at the Department of Mechanical & Aerospace Engineering, at UCSD (2013), where I met and worked with the legendary Prof. Walter Munk (Einstein of the Ocean). Then I became a Visiting Scientist & Research Fellow/postdoc, at the Department of Mechanical Engineering, MIT (2013-2015), where I worked with Prof. T.R. Akylas; and an Assistant Prof. at Haifa University and a Visiting Assistant Professor at the Department of Mathematics, MIT (2015-2016) hosted by Prof. John Bush and worked closely with Prof. C.C. Mei from CEE. I moved to the UK and joined Cardiff University’s School of Mathematics (tenured position) in 2016, keeping an honorary Research Affiliation at MIT (2016-2020). In 2018 I became a Visiting Assistant Professor at the School of Mechanical and Material Engineering, University College Dublin.
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