Published online by Cambridge University Press: 21 May 2007
The complex flow features that arise from the impact of a shock wave on a concave cavity are determined by means of high-speed video photography. Besides additional information on features that have previously been encountered in specific studies, such as those relating to shock wave reflection from a cylindrical wall and those associated with shock wave focusing, a number of new features become apparent when the interaction is studied over longer times using time-resolved imaging. The most notable of these new features occurs when two strong shear layers meet that have been generated earlier in the motion. Two jets can be formed, one facing forward and the other backward, with the first one folding back on itself. The shear layers themselves develop a Kelvin–Helmholtz instability which can be triggered by interaction with weak shear layers developed earlier in the motion. Movies are available with the online version of the paper.
Movie 1. Schlieren imaging of a Mach 1.04 shock interacting with the cavity, showing the transition from the incident wave, through the focusing phase, to the development of the main reflected wave. Framing rate = 500 kfps. Model A.
Movie 2. Propagation of a Mach 1.33 incident shock showing the wavelets generated from thin tape positioned on the wall. Framing rate = 250 kfps. Model A.
Movie 3. Shadowgraph record of a Mach 1.24 shock wave reflecting off the cylindrical surface. The reflection pattern changes from a reflected compression wave, to a Mach Reflection, MR, followed by a Transitioned Regular Reflection, TRR. Framing rate = 500 kfps. Model B.
Movie 4. Flow features following interaction for a Mach 1.35 incident shock, showing the development of the jets and the Kelvin-Helmholtz instability on the shear layer, including the weak shear layer that triggers an instability. Framing rate = 250 kfps. Model A.