Flow Visualization of Planar Blast Waves Discharging from a Suddenly Expanded Duct

Abstract

The interaction of a planar blast wave with vortices is one of the fundamental and important topics in shock wave dynamics, since the problem is closely related to the aerodynamic noise generation in high-speed aircraft and the noise emitted from a vehicle's exhaust system or an internal combustor. In this study, the problem of a planar blast wave discharged from a suddenly expanded duct is considered. A high-resolution Euler solver developed by a 5(superscript th)-order WENO scheme of Jiang and Shu is employed to investigate this problem. The present Euler solver is validated to be reasonably accurate. For the problem of a blast wave passing through the duct with a sudden expansion is studied in detail. The induced vortices induced by the first shock wave are respectively arranged to interact with the second shock wave and a reflected shock wave at a different time sequence. We found that the trajectory of the vortex centers is affected by the expansion waves issuing from the sharp corner of another small vortex ring. Moreover, the problem of different-intensity blast wave propagating in a duct with a sudden expansion is numerically investigated. In order to see possible vortices generated by blast/vortex interactions, we use two techniques, namely, computational shadowgraph, arid computational schlieren. It is found that the computational schlieren is better for identifying the flow structure induced by shock/vortex interaction.