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We consider two cases of interaction between a planar shock and a cylindrical density interface.In the first case (planar normal shock), the axis of the gas cylinder is parallel to the shock front, and baroclinic vorticity deposited by the shock is predominantly two-dimensional (directed along the axis of the cylinder). In the second case, the cylinder is tilted, resulting in an oblique shock interaction, and a fully three-dimensional shock-induced vorticity field. The statistical properties of the flow for both cases are analyzed based on images from two orthogonal visualization planes, using structure functions of the intensity maps of fluorescent tracer pre-mixed with the heavy gas.At later times, these structure functions exhibit power-law-like behavior over a considerable range of scales. Manifestation of this behavior is remarkably consistent in terms of dimensionless time τ defined based on Richtmyer's linear theory within the range of Mach numbers from 1.1 to 2.0 and the range of gas cylinder tilt angles with respect to the plane of the shock front (0 to 30 • ).

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A cylindrical, initially diffuse density interface is formed by injecting a laminar jet of heavy gas into the test section of a shock tube. The injected gas is mixed with a fluorescent gaseous tracer, small liquid droplets, or smoke particles. The shock tube is tilted with respect to the horizontal. Thus the axis of the gravitystabilized heavy gas jet is at an oblique angle with the plane of the arriving shock front. The flow structure forming after the oblique shock wave interaction with the column of heavy gas is revealed by visualization in multiple planes. We observe the formation of the well-known counter-rotating vortex columns (same as caused by normal shock waves). However, along with them, periodic co-rotating vortices form in the vertical plane in the flow downstream of the oblique shock. The size of these vortices varies both with the Mach number and with the initial angle between the column and the shock front.

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When a shock encounters a multiphase interface at an oblique angle, threedimensional (3D) flow effects are produced. Experiments using advanced optical diagnostics seek to elucidate the 3D nature of the flow as it transitions to turbulence. Planar laser-induced fluorescence (PLIF) images capture the development of flow instabilities in a shock-accelerated heavy gas column. Early time images show the counter-rotating vortex pair (CRVP) associated with the Richtmyer-Meshkov instability (RMI) both for normal planar and for oblique shocks, with the cores of the vortex pair parallel to the axis of the original gas column. For the oblique case, a shear-driven Kelvin-Helmholtz instability (KHI) also develops along the axis of the column due to 3D vorticity deposition. The influence of inclination angle of the column with respect to the shock direction on this secondary instability and thus upon the fully 3D flow, is assessed. The 3D data collected in these experiments is essential to the validation of numerical codes predicting a range of problems from scramjets to supernovae.