Visualization of over-expanded supersonic wall-jet

An experimental study has been conducted to understand the near flowfield of an over-expanded supersonic wall-jet (Mach number = 1.7 and unit Reynolds number = 2.13×107 m−1). The primary and secondary shocks of both free-jet and wall-jet have been studied in detail. The flow features are captured with shadowgraphy, oil flow visualization and infrared thermography. Since both oil flow visualization and infrared thermography have been used for surface flow visualization, a comparative study is also performed between oil flow visualization and infrared thermography. This reveals their ability to capture supersonic surface flow features like shock-wave/boundary-layer interaction, expansion-wave/boundary-layer interaction, separation bubble and shear layer growth on the wall. The merits and demerits of the two methods are listed.