抄録
Large scale recirculating flow in a river was measured by a new image analysis method, Large Scale Particle Image Velocimetry (LSPIV), proposed by one of the authors. In this method, oblique-angled video images of river surface flow visualized by special tracer can be analyzed by PIV after the geometric image transformation. In this research, accuracy of the image correction was improved by introducing three-dimensional information of mark point coordinates.This method was applied to the surface flow between the five groins installed in the Nagara River in Japan. It was demonstrated that large-scale surface flow structure could be clearly visualized by the superposition of particle images.
In addition, the characteristics of the surface flow were made clear from the surface velocity distributions obtained by LSPIV.
