New optical tools for fluid mechanics

Optical flow measurement is the most important non-intrusive technique in fluid mechanics. A second advantage of some new optical measurement techniques is the high resolution in space and time. As a third advantage, flow visualisation also has a special importance in fluid mechanics. The unsteady three-dimensional flow fields need a visual display of experimental as well as theoretical results. Optical visualisation techniques often lead to completely new insights in flow phenomena especially in experiments. Some discoveries which have been made this way are mentioned here.