Application of PIV to Surface Flow Measurements Between Groins

Abstract

A new PIV technique is proposed for the measurement of river flows. In this method, environment-friendly tracers made from corn starch, normally used as shock absorbers, were used for visualizing the surface flow Oblique-angled tracer images were taken from the river bank, which were then transformed to non-distorted images before the PIV analysis by using a mapping function. A new feature of the method is the introduction of threshold level that detects only the tracers; only those templates containing a portion of tracers were used in the PIV analysis. The application of the method to the flow between the groins in the Nagara River revealed the existence of complicated re-circulating flows.