Date & Time: Tuesday, November 19, 2013, 16:00-17:00.
Venue: Ramanujan Hall

Speaker: Régis Marchiano, Université Pierre et Marie Curie

Title: Singular Nonlinear Acoustics

Abstract: A fascinating branch of wave theory deals with the properties of singular waves. A wave is defined by its amplitude, phase and polarization. If one of these quantities is undefined (singular), spectacular properties can arise such as the formation of rainbows for optical waves or the superboom for acoustical ones. For linear waves, amplitude and phase singularities can be described independently from the kind of wave (optics, acoustics, ...). If waves are nonlinear, manifestations of singularities depend on the wave type. In this presentation, we deal with nonlinear singular acoustics in fluids (only amplitude and phase singularities are discussed). Special attention is paid to two examples: focusing of shock waves on caustics (amplitude singularity) and nonlinear acoustical vortices (phase singularity). Models, numerical simulations and experiments are presented.