Stray light measurement in air for the visualisation of air flow in rotating cavities

Flow measurement in rotating cavities using tracer particles (1-10 mu m particle size) can be tampered by the centrifugal force. Methods like LDA or PIV may fail for that reason. The air flow in the rotating cavity is visualised by injected smoke (0.01-1 mu m) and stroboscopic lightening. Smoke particles are too small and too highly concentrated for LDA and PIV. Smoke concentration data with good resolution (time, locality) is shown to be achieved using video recording and image processing. This provides also information about the flow in the rotating cavity.