Schlieren Techniques in Comparison: The Background Oriented Method versus Visualization with Holographic Filters.

Within this paper two recently developed visualization techniques are presented. The results of the Background Oriented Method, are compared to the flow-field visualizations, obtained by using the holographic filters from ISL. Both, the background oriented schlieren technique as well as the visualization with holographic filters were used to represent the index gradients of aerodynamic flows. The investigations have been carried out in the ISL blow-down wind tunnel at a Mach number of 3. A canard-wing configuration was used in order to study the shock-vortex interaction phenomenon. Background Oriented Schlieren Technique (BOS) The background oriented schlieren technique can best be compared with the density speckle photography as described by Debrus et al. (1972), Kopf (1972), and in an improved version by Wernekinck and Merzkirch (1987). The method described here, is based on a patent hold by Meier (1999), for detailed information see Richard and Raffel (2001). Fig. 1: Optical set-up for the background oriented schlieren technique (BOS) E. Augenstein Lehrstuhl Aerodynamik und Stromungslehre, Brandenburgische Technische Universitat, Cottbus, Germany F. Leopold French-German Research Institute of Saint-Louis (ISL), Saint-Louis, France H. Richard, M. Raffel Institut fur Stromungsmechanik; DLR, Gottingen, Germany Correspondence to: Dr. Edgar Augenstein, Lehrstuhl Aerodynamik und Stromungslehre, Brandenburgische Technische Universitat, Postfach 10 13 44, D-03013 Cottbus, Germany, E-mail: edgar.augenstein@las.tu-cottbus.de