Flow visualization using reflective flakes

Abstract

AbstractThe pattern in an image of flow visualizations using reflective flakes stems from their non-uniform orientation rather than their spatial accumulation. It is shown, based on the assumption that flakes are infinitely thin elliptic discs without inertia, that the temporal evolution of their orientations is identical to that for infinitesimal material surface elements. In general, bright regions in a visualized image are the superposition of those where the flake (i.e. the material surface element) orientation is isotropic and those where flakes tend to align in the direction for which the incident rays are reflected into the line of sight. A non-trivial example of the visualization of a steady flow in a precessing sphere is given to verify these conclusions.