Development of a quantitative Schlieren imaging technicque for acoustic waves

Abstract

The primary objective of the present work was the development of a quantitative schlieren-imaging technique that can be used to study the dynamics of instability waves. An underexpanded jet was considered as an ideal test case due to the complexity and multitude of instability mechanism. The technique was initially validated by optically capturing a controlled acoustic wave generated by a compression driver and excellent agreement was obtained with microphone measurements. Further analysis of an underexpanded jet demonstrated that the technique can be used to capture the very high screech frequency