Hierarchical Recursive PIV (HR-PIV) method, which can get a very high spatial resolution compared with conventional PIV image processing methods, was used to do PIV image processing of a jet mixing flow. By starting with a large interrogation window size and search distance as the same as conventional correlation analysis based PIV image processing methods, HR-PIV method improved the spatial resolution of the PIV result through hierarchical reduction of the interrogation window size and search distance in the next iteration step by using the calculation results of former step. It was found that the small scale vortices and turbulent structures in a jet mixing flow, which can not be identified by using conventional PIV image processing methods, can be revealed very clearly by using Hierarchical Recursive PIV (HR-PIV) method
