Formation and scaling of vortex dipoles generated from shock-accelerated interfaces*

Vortex dipoles are known to emerge in a variety of flows relevant to astrophysics, high energy density physics, and inertial confinement fusion, where they can significantly affect the flow through the transport of vorticity. We systematically study the generation and scaling of such dipoles utilizing a numerical platform involving a shock passing through a grooved interface separating two dissimilar fluids. As the shock passes through the interface, it deposits baroclinic vorticity that induces a complex phase inversion process ultimately resulting in the ejection of a dipole. By modulating the aspect ratio of the groove, the amount of vorticity in the flow available to the dipole is controlled. Based on the aspect ratio of the groove, we find that two distinct flow regimes emerge. For small aspect ratios, a single dipole is generated that contains the majority of the vorticity deposited by the shock. Beyond a critical groove aspect ratio, however, the circulation of the ejected dipole saturates, and the additional vorticity in the flow accumulates in a jet that trails the leading dipole. This behavior suggests the existence of fundamental formation number governing the scaling of dipoles generated from shock-accelerated interfaces, including those in Richtmyer-Meshkov flows.