Complex flow morphologies in shock-accelerated gaseous flows

A Mach 1.2 planar shock wave impulsively and simultaneously accelerates a row of three heavy gas (SF6) cylinders surrounded by a lighter gas (air), producing pairs of vortex columns. The heavy gas cylinders (nozzle diameter DD) are initially equidistant in the spanwise direction (center to center spacing SS), with S/D=1.5S/D=1.5. The interaction of the vortex columns is investigated with planar laser-induced fluorescence (PLIF) in the plane normal to the axes of the cylinders. Several distinct post-shock morphologies are observed, apparently due to rather small variations of the initial conditions. We report the variation of the streamwise and spanwise growth rates of the integral scales for these flow morphologies.