Shock Wave Development Within Expansive Flows
The propagation of two-dimensional expansion waves over a corner has received very little attention in the past. It can be studied experimentally in a standard shock tube by placing the test section at the end of the high-pressure section rather than the conventional method with placement at the driven section. It is found that reflected compression and shock waves can form as the wave propagates over the corner. An attached flow separation bubble develops at the corner and for a strong enough wave can develop a region of supersonic flow above it, and, in some cases, a transonic shock wave. Furthermore, for a sufficiently strong expansion wave, the flow behind the trailing edge of the expansion wave becomes supersonic. It has also been shown that when an expansion wave reflects off a wedge, shock waves can also develop due to the induced velocity flowing down the surface of the wedge striking the corner. The development of shock waves can also occur if the expansion wave focuses on a cavity.
The results of projects from a number of undergraduate and postgraduate students, which have been included, are gratefully acknowledged. The support from the National Research Foundation in supporting these projects, either in the form of bursaries or for project costs is much appreciated.