Visualization of very weak shock waves by digital phase-shift interferometry

In this study, the method of digital phase shift holographic interferometry is applied to accurately measure the density distribution behind a weak shock wave. The goal of this investigation is to visualize and quantitatively evaluate flow fields behind weak disturbances, which are only marginally stronger than sound waves. In the present experiment, the shock Mach number was approximately Ms approximately equals 1.01. The wave was generated by the explosion of a small silver-azide (micro- charge) pellet, which was ignited by an Nd:YAG laser. Using phase shift interferometry, the phase distribution of the region far behind the incident shock could be detected.