In the past the Paul Vielle lecture has taken one of two formats, either the exposition on a single topic, such as by Ben-Dor in 2013, or an overview of a range of topics covering work from a single institution or group, such a that by Takayama in 2011. This paper is similar to the latter, and will cover a range of experimental studies, some successful, some not, and some started and never completed; done over a number of years in what is now the Flow Research Unit at the University of Witwatersrand.
The work covers a number of different aspects covering studies in liquids and deformation of solids using liquid shock waves, but the primary focus has been investigation of the behaviour of gas dynamic shock waves. It a number of cases it has lead to the development of unusual and unique experimental facilities and diagnostic techniques, such as the tracking of very weak perturbations to clarify flow behaviour, as indicated in Fig 1a.
A particularly challenging area has been the largely ignored area regarding the reflection of very weak shock waves. This is partly due to the perceived limited applications but also because of experimental difficulties relating to limited resolution and test reproducibility. However, some sucess has been achieved as shown in Fig. 1b.
The benefits of using symmetry in experiments in both steady and unsteady flows is demonstrated, both in the context of the von Neumann Paradox and the influence of moving wedges.
A more limited series of studies have been conducted using liquids, both in the development of liquid jets (Fig 1c), the use of low sound speed liquids and experiments using the hydraulic analogy.
The examples given above represent a limited selection of the experiments that are to be discussed.
