On the Evolution of Double Shock-Accelerated Elliptic Gas Cylinders

The evolution of double elliptic heavy-gas (SF6) cylinders impacted by a planar shock wave is studied by high-speed camera diagnostics. The minor axes (b) of the elliptic cross sections are aligned perpendicular to the shock direction. While the cylinder dimensions are fixed, we adjust the center-to-center separation s between the cylinders. The resulting flow morphologies are visualized and the interaction between double cylinders is analyzed. When s/b = 4.0 or 3.0, the two elliptical cylinders roll up into two counter-rotating vortex pairs and their interaction is weak. When s/b decreases to 2.0 or 1.2, due to strong interaction of the two inner vortices, the inner structure completely disappears and the flow morphology evolves into one counter-vortex pair. Compared with the s/b = 2.0 case, larger amount of baroclinic vorticity is produced in the s/b = 1.2 case, and the morphology is similar to the single elliptic cylinder case, with a second vortex phenomenon occurring at later times. As s/b increases, the extent of cylinder-cylinder interaction becomes weaker, and the integral height of double elliptic cylinders grows while the length decreases.