Shock-Bubble Interaction

When a shock wave propagates across the interface between fluids of different acoustic impedance, two fundamental events follow: the refraction of the shock wave across the non-uniformity, and the baroclinic generation of vorticity on the interface. This latter, in turn, causes the development of distinct vertical structures which lead to the distortion and eventual breakup of the original interface shape, and ultimately the mixing of the two fluids. In this talk, I will describe the results of laboratory experiments for the study of shock-accelerated spherical interfaces (soap bubbles filled with a gas different than its surroundings). This particularly simple geometry falls within the broader category of "shock-accelerated inhomogeneous flows", examples of which occur over very large ranges of geometrical and energy scales: from the overturn of supernova cores, to the implosion of microtargets in experiments aiming at nuclear fusion by inertial confinement. In our experiments, a soap bubble, filled with one of a variety of different gases, is released to move freely in an inert gas inside a vertical shock tube until a downward-moving, planar shock wave strikes the bubble. Both non-reactive and reactive bubbles are studied. Numerical simulations with the Raptor code are also performed. The results I will present include: scaling parameters for the time history of macroscopic length scales; evidence of compressibility effects; estimates of peak temperature and pressure values from measurements of the ignition delay.

Speaker: Riccardo Bonazza, Univ. of Wisconsin - Madison

Room 300