Mechanical and Civil Engineering Seminar

Mechanical and Civil Engineering Seminar Series

Title: Vortex Dynamics in Inertial Fusion and Supernovae

Abstract: The mixing induced by a shock wave passing through a fluid interface can stimulate the ejection of high-velocity projectiles of one fluid into the other, which severely disrupt implosion symmetry in inertial confinement fusion (ICF) and transport stellar core elements during supernovae. Recent improvements in experimental diagnostics and numerical simulations reveal that such projectiles share key characteristics with classical fluid vortex rings, thus enabling a path to understand their dynamics. Our objective is to isolate the ejection of vortex rings from shocked interfaces and determine their scaling through numerical simulations and physical experiments. We find that the strength of the rings expectedly scales with the intensity of density and pressure gradients but saturates beyond a critical protrusion size, enabling an a priori prediction of the energy transported by vortex rings in ICF and supernovae.

Vortex dynamics may have also shaped the environment surrounding the progenitor of Supernova 1987A, which consists of evenly spaced gaseous clumps immersed in an equatorial ring. Our analysis suggests that the ring could have formed an unstable vortex dipole after acquiring vorticity from the progenitor wind, with a dominant wavenumber remarkably consistent with the number of observed clumps. Recent observations by the James Webb Space Telescope further confirm the plausibility that the Crow instability induced clump formation.

Bio: Michael Wadas is the Cecil and Sally Drinkward Postdoctoral Scholar in the Mechanical & Civil Engineering Department at Caltech, where he is advised by Tim Colonius and Joseph Shepherd. His research combines theory, simulations, and experiments for the study of both high-energy-density and classical fluid flows and has led to techniques for strengthening laser-driven shock waves, an experimental platform for generating high-energy-density vortex rings, a novel interpretation of clumping in circumstellar environments, and an enhanced understanding of instability mechanisms in accelerated interfacial flows. Michael received a B.S. in Mechanical Engineering from Purdue University in 2017 and a Ph.D. in Mechanical Engineering from the University of Michigan in 2023.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors.