Chapter 5.1 - Measurement Techniques and Diagnostics: 5.1 Flow Visualization

Abstract

This chapter discusses flow visualization with density-sensitive flow visualization, the shadow technique, Schlieren method, color Schlieren techniques, and direction-indicating color Schlieren method. The most commonly used techniques to visualize compressible fluid flows utilize a fundamental physical principle–the fact that the speed of light depends on the density of the (transparent) medium it traverses. A great number of techniques are developed since flow visualization was recognized as an eminently important discipline to study fluid mechanics, with its capability to yield both qualitative and quantitative information regarding the flows under investigation. the development and application of some visualization methods is crucial in helping to detect and understand fundamental mechanisms of shock wave propagation and interaction. The importance of flow visualization as a diagnostic tool has even increased throughout this century, with visualization techniques often being the sole, or at least the main, suppliers of information about a flow field. The optical techniques described in this chapter are also relevant for another important reason: as they are nonintrusive, allowing one to take measurements within a flow field without disturbing or influencing it.