Techniques of Flow Visualization

The techniques of flow visualization and their application in wind tunnels, water channels, and experiments related to propulsion research are reviewed. These techniques can be classified roughly into three major groups Surface flow visualization, scattering from flow tracers, and density sensitive flow visualization. The progress in laser optics and the wide-spread use of computers has led to the development of novel techniques and evaluation procedures, which are included in the review e.g. laser-induced fluorescence, speckle photography, image processing, and optical tomography. Emphasis is given to the discussion of the physical background of the methods. Information on technical details is provided by means of a number of sample photographs and by respective references.