A combination correlation-based interrogation and tracking algorithm for digital PIV evaluation

Abstract

A combination of the correlation-based interrogation algorithm and the correlation-based tracking algorithm is proposed for digital PIV evaluation. A zero-padding interrogation algorithm is adopted in which the interrogation windows differ in size and in which the number of pixels in the side length of the smaller window is not restricted to a power of 2. This greatly improves the algorithm's accuracy and measurement range. The correlation-based tracking algorithm is employed when the already-measured vector can serve as a good predictor of the next vector to be measured. In this case, only a very small searching scope is required and computation can be fast. Computational intensity analysis shows that, using the same-sized sampled window, the correlation-based tracking algorithm is more efficient than the conventional correlation-based interrogation algorithm if the searching scope is less than 4. Compared with some of the other correlation-based algorithms, the proposed combination method is faster, is more accurate, has a larger measurable range, and can utilize a sampled window of any size.