Visual determination of the onset of irregular blast wave reflection

This paper presents further results of an ongoing experimental and numerical investigation into the unsteady process of blast wave reflection from straight smooth surfaces. It is shown that basic blast wave phenomena such as the transition from regular to irregular wave reflection can be adequately and conveniently studied in a laboratory environment by using small charges with masses in the milligram range. While the laboratory scale generally provides greater accessibility, it also imposes more stringent conditions on the diagnostics than the large-scale environment. The paper reviews the previously found considerable discrepancies between numerical and experimental results for the location xtr of the transition from regular to irregular wave reflection. These are caused by the initially minuscule size and gradual growth of the Mach stem and the limited resolution of the recording material. Different techniques are used to improve the accuracy of the experimental determination of the transition point, and a new combination of modern high-speed photography with the traditional soot technique is shown to be the most promising tool for this purpose.