開水路流れの大規模乱流構造と構造物周辺の局所流との関連について

Abstract

The stability and the transversal scale of secondary flows in an uniform open channel floware examined by using the flow-visualizing techniques. Important results are obtained that thelarger friction velocity brings stabler secondary flows.The local flow just upstream side of a broad crested weir is also examined with the intentionof clarifying the three-dimensional characteristics of it. It is shown that the local flow is charac-telized by U-shaped vortices which are arranged in a transversal direction. The scale, position, strength and fluctuation of the U-shaped vortices are measured experimentally and the resultsare examined to conclude that they have a close relation with those of the secondary flows in anapproaching flow.Experimental study is also made on the local scour just upstream side of an broad crestedweir. The results show that the scale of the scour hole is wavy in a transversal direction due tothe effect of secondary flows.