Power-filter technique for modifying depth of correlation in microPIV experiments

A new image filtering method, termed power-filtering, is proposed for use in microscopic particle image velocimetry (PIV) to control the depth of correlation, independent of the image acquisition system, particle size, and flow characteristics. An analytical model of the depth of correlation for the filtered images is developed and verified with a series of careful experiments. This model predicts that the depth of correlation can be increased or decreased by a factor of two by applying power-filter values of 0.63 and 2.0, respectively. Experiments show that the analytical model for the power filtering technique is generally accurate to within the measurement uncertainty.