Image analysis on velocity fields in a permeable weir

Recently, permeable river structures such as a rubble mound weir attract attention from an environmental point of view. A permeable structure minimizes negative impact on natural environment compared to conventional solid structures made of concrete and steel. This type of weir purifies water through aeration as well as provides passage of aquatic lives in the longitudinal direction. In order to evaluate these environmental functions, it is necessary to analyze internal flow in the structure.In this study, flow fields in a rubble-mound weir were visualized by adjusting refractive index between solid-fluid phases. The flow velocity and turbulence are measured from image analysis, and the flow properties inside rubble-mound was analyzed. The present research will be useful in making hydraulic design of a permeable rubble mound.