Development of PIV measurement technique in turbulent flow laden with binary-size particle groups

Particle image velocimetry (PIV) is an instantaneous whole-field measuring diagnostic that makes it feasible to measure the microscale spatial information of the interphase dynamics for good understanding of two-phase flow. However, application of PIV to the two-phase flowmeasurement is still a state of the art so far. Adouble-discriminating process in terms of gray level and size of image patterns togetherwith themedianmask technique is developed. The test flowis a turbulent air wake ladenwith a binary group of particleswith the mean size of 2.7 mu m(representing the carrier phase) and 55 mu m (representing the dispersed phase). It is demonstrated that the velocity measurements of both phases can be successfully performed through the combined PIV/PTV (particle tracking velocimetry) scheme associated with the developed phase discrimination method. It is noted that the discriminating capability of the size ratio between the large- and small-particle groups in the study is around 20 together with themean size ofO(10(0) mu m) for small particles, which is the commonly required size for the seedings used in the PIV measurements of airflows, as compared to the size of O(10(1) mu m) adopted in the current two-phase PIV measurement methods.