Unsteady shock wave diagnostics with high-speed imaging.

摘要

The visual study of unsteady shock wave dynamics has in the past predominantly been done using single-shot images.The advent of ultra-fast, good-resolution high-speed digital cameras has changed this state of affairs and allows the truedevelopment of the flow to be studied. It enables the detection of weaker features which are easily overlooked in single-shot visualizations by virtue of the fact that human vision is very sensitive to detecting the motion of an object, even if itgenerates only a faint optical signal. Recent application of these devices to the study of the focusing of a shock wave in acylindrical cavity has identified a number of previously unknown features, while other features that previously had beeninadequately reported could be clearly identified and explained The observation of deliberately generated weakdisturbances allows the quantification of which part of the flow is influenced by which part of the boundariesencompassing it. Whilst the imaging itself is very useful it is also highly desirable to use techniques from whichquantitative data can be obtained. Color, such as in direction- and magnitude-indicating color schlieren, and polychromeshearing interferometry, adds an additional dimension to such investigations.