複断面蛇行開水路流れの構造と低水路の河床形態に関する研究

Abstract

複断面蛇行開水路流れの構造は, 相対水深(Dr=高水敷上水深/低水路水深)などの流れの条件, 蛇行度などの幾何条件に支配され, 複雑な様相を呈する。本研究では, 速度計測, 横断面流況の可視化, 掃流力分布の可視化, および河床形状の計測などで得られる結果を用いて, 流れの構造を検討するとともに, 掃流力分布との関係や河床の洗掘・堆積現象との関係について検討を加えた。その結果より, 低水路が固定床の場合の2次流構造, それが掃流力分布に与える影響, 移動床とした場合の構造の変化などを指摘している。

Over-bank flow in a straight channel with a sinuous main channel is discussed based on experimental results.The flow structure is characterized by secondary flow and fluid mixing between the main channel andflood plain flow. The secondary flow was directly visualized by a submergible video camera. The secondary flow shows spiral motions and affects the distribution of boundary shear stress and sediment transport. The relation between these structure and the traction process of bed materials is discussed on the basis of the distribution of tractive force visualized by a new method .We also made experiments in a channel of which main channel was movable bed. The secondary flow forms three distinct eroded regions and two deposited regions on the bed. Those regions are formed by the secondary flow.