STUDY ON IMPROVEMENT OF RETURN FLOW TYPE UNDERWATER REDUCER AND UNDERSTANDING OF FLOW STRUCTURE BY IMAGE ANALYSIS

Abstract

 This study is a hydraulic model experiment aimed at improving the economically advantageous reduction system and compacting the reduction section as a reduction gear for the spillway of a hydroelectric power plant. The return-flow type underwater reducer consists of a perforated deflector and endwalls that reduce momentum through complex interactions of flows. This method is mainly applied to underwater force reduction of dam outflow facilities, and has the advantages of less noise and fog generation due to reservoir outflow, but has disadvantages in construction and maintenance of deflectors due to the narrow spacing of the holes. This study conducted hydraulic model experiments on deflectors (slit case, etc.) and compacting force-reducing sections to understand (1) the maximum water level, (2) water level fluctuation, and (3) velocity vectors by image analysis. As a result, this study understands the flow structure and momentum reduction effect, and proposes an improvement system in terms of constructability, cost reduction, etc.