Unexpected features in shock-driven hydrodynamics

Abstract: 

A good physical understanding of shock-driven mixing flows is important for a rather wide variety of areas, including astrophysics, inertial confinement fusion, and nuclear stockpile stewardship. Recent studies reveal several new aspects of these flows. While theory is best developed for a case when a shock wave accelerates an initially perturbed interface between two fluids (or gases), real-world flows of interest are frequently characterized by the presence of multiple phases in the shocked media. For example, supernova explosions propagate through dusty interstellar gases or plasmas. An impulsively driven instability developing on an interface between two gases or fluids without multiphase inclusions is named after its co-discoverers, Richtmyer and Meshkov, and is well known since the 1960s. It is, however, still a matter of discussion how to name its multiphase analog, whose existence was first convincingly demonstrated in 2011, and which has both similarities with Richtmyer-Meshkov instability and physically important distinctions from it. Another underappreciated aspect of shock-driven flows that can be observed in experiments both for mixing gases and for multiphase media is transition to turbulence characterized by scalings that manifest considerable differences with theory for fully developed turbulence, and while plausible physical explanations for these differences exist, a lot of work is still required to fully understand the results. Finally, many flow structures forming in shock-driven mixing still deserve a more thorough study – both for their effect on mixing and because they are so pretty.