The application of particle image velocimetry to high speed flows

Particle Image Velocity (PIV) is now a well established, non-intrusive technique for the two dimensional measurement of fluid velocity from a single plane of interest within a fluid flow. This thesis presents new work into the application of the double pulsed PIV technique to highspeed flows. The areas of work can be split into three major areas. The first area of work involved a comprehensive study into data reduction using autocorrelation. Results from the study allowed the development of an optimisation method which provides a consistent basis for experimental design. Further work validated this method by comparing equivalent results from sets of PIV transparencies processed using a system developed from commercially available image processing equipment. The second area of work involved supersonic flow studies of a de Laval expansion nozzle. PIV results were recorded from both inside and outside the nozzle. Inside the nozzle the PIV results resolved a normal shock and allowed comparisons with a 1D theoretical model, a CFD prediction and Schlieren photographs. Outside the nozzle the PIV data permitted overexpanded jet shock cell structures to be resolved and compared to a shock cell model. The final area of work involved development of an image labelling system for high speed flows by changing the transfer characteristics of the recording optics between exposures. A general theory of this technique was developed and a system designed and tested which can be applied to flows of arbitrarily high speed.