Single pixel resolution correlation applied to unsteady flow measurements

In standard particle image velocimetry, the spatial resolution of the velocity field depends on the final window size of the cross-correlation. For small and micro experimental configurations, the PIV measurement is often limited by the optical accesses, the depth of focus and the number of particles in the interrogation window. With the aim of obtaining a resolution of one vector per pixel, a single pixel resolution correlation (SPRC) algorithm is described and applied to the study of a Poiseuille flow that is steady on average between two close walls, one of which has grooves normal to the streamwise direction. The influences of the number of real images and the application of different thresholds to the correlation are discussed. From 10,000 double frames, the velocity field is calculated by the SPRC and compared to the mean velocity field calculated by standard cross-correlation.