Schlieren and cross-schlieren imaging for quantitative flow visualization

The schlieren imaging is a fundamental flow visualization technique applicable to combustion flame and high-speed flows. In this talk, some applications of the schlieren imaging are shown to understand the flow physics. They include the flickering combustion flame under acoustic excitation, screech tone phenomenon from underexpanded supersonic jet and the shockwave formation in a cavitating jet. Furthermore, the development of the schlieren for quantitative flow visualization is examined by introducing the cross-schlieren imaging and the usefulness of this experimental technique is studied.