Hydrodynamics of Shocked Interfaces

Michael Wadas, University of Michigan

Photo of Michael Wadas

Shock waves occur in compressible flows following large and sudden disturbances, such as the detonation of mining explosives or the rapid transit of a high-velocity aircraft. When these waves interact with material interfaces, they may become attenuated or strengthened, and the mixing they induce has critical implications in many scientific and engineering contexts. For example, shock-induced mixing of astrophysical materials naturally follows supernova explosions and may govern the structure of any ensuing nebula. Furthermore, in inertial confinement fusion (ICF), mixing leads to a reduction in compression that severely penalizes fusion yields. The focus of the present work is improving our understanding of these complex interfacial hydrodynamics to advance astrophysics, fusion research, and many other applications. Specifically, a technique is developed for strengthening shock waves in laser compression experiments by carefully designing a sequences of material interfaces through which the shock must pass prior to its arrival at the sample under study. This technique can be readily applied to existing laser facilities, enabling up to a twenty-five percent increase in shock pressures for some materials, and is also applicable to several inertial fusion concepts, including double-shell and revolver ICF targets. In addition to our work on shock strengthening, we present our scaling theory for vortex rings ejected from shocked interfaces. Such rings have long been observed in both experiments and simulations of the Richtmyer-Meshkov instability (RMI). Furthermore, they have been shown to be a vehicle for the transport of a significant amount of energy from the interfacial mixing region, which may have critical implications for the transition of the flow to a state of turbulence. In addition to the RMI, our scaling is applicable to flows involving shock-induced interfacial jetting, such as experiments exploring astrophysical jets, ejecta physics, and ICF fill-tube dynamics.

Abstract Author(s): Michael Wadas