Experimental study of shock-accelerated inclined heavy gas cylinder

Abstract

An experimental study examines shock acceleration with an initially diffuse cylindrical column of sulfur hexafluoride surrounded by air and inclined with respect to the shock front. Three-dimensional vorticity deposition produces flow patterns whose evolution is captured with planar laser-induced fluorescence in two planes. Both planes are parallel to the direction of the shock propagation. The first plane is vertical and passes through the axis of the column. The second visualization plane is normal to the first plane and passes through the centerline of the shock tube. Vortex formation in the vertical and centerline planes is initially characterized by different rates and morphologies due to differences in initial vorticity deposition. In the vertical plane, the vortex structure manifests a periodicity that varies with Mach number. The dominant wavelength in the vertical plane can be related to the geometry and compressibility of the initial conditions. At later times, the vortex interaction produces a complex and irregular three-dimensional pattern suggesting transition to turbulence. Highly repeatable experimental data are presented for Mach numbers 1.13, 1.4, 1.7, and 2.0 at column incline angles of 0 $$^{\circ }$$ , 20 $$^{\circ }$$ , and 30 $$^{\circ }$$ for about 50 nominal cylinder diameters (30 cm) of downstream travel.