Analysis and treatment of errors due to high velocity gradients in particle image velocimetry

摘要: This paper deals with errors occurring in two-dimensional cross-correlation particle image velocimetry (PIV) algorithms (with window shifting), when high velocity gradients are present. A first bias error is due to the difference between Lagrangian displacement of a and real velocity. calculated theoretically as function gradients, shown reach values up 1 pixel if only one translated. However, it becomes negligible both windows shifted symmetric way. second source linked pattern deformation, which decreases height correlation peaks. In order reduce this effect, deformed according an iterative process. The problem finding sufficiently reliable starting point for iteration solved by applying Gaussian filter images correlation. Tests PIV algorithm based on these techniques performed, showing their efficiency, allowing determination optimum time separation given field. An application new experimental containing concentrated vortices shown.