New Dimension in the Schlieren Technique: Flow Field Analysis Using Color

Abstract

The various techniques for introducing color into a schlieren system were explored, and all of them were found to have drawbacks such that the added dimension of color in a schlieren has never been utilized for extensive quantitative measurements. An entirely new technique using a diffraction grating to produce the color has been introduced as a modification of the conventional schlieren system. It provides solutions to the problems of sensitivity, range of measurement deflection and undesirable effects of diffraction which have limited the usefulness of color systems in the past. Methods for analyzing a conventional schlieren have been modified for the analysis of a color schlieren result. Surface pressures and flow field analysis for some simple two-dimensional airfoil shapes have been obtained by these color techniques developed here, and the results compare very well with theoretical pressure calculations.