開水路断面変化部における流れの水理特性について (3) -段上り部および段落ち部に関する実験的検討-

Abstract

This paper deals with an open channel flow through an abrupt bed depression or ascention.Characteristics of the length of seperation region, velocity distribution, dominant period of turbu-lence, turbulent energy balance and bed shear stress are investigated experimentally. Themeasurement of velocity and bed shear stress are made by hot-film flowmeter.Main experimental results obtained are follows; For a flow through abrupt bed depression, 1) The length of seperation region under submerged transition depends on the ratio of depressionheight and up-stream depth, and Reynolds number defined by depression height and mean velocityof approaching flow. 2) The distribution of bed shear stresses depends on the kind of flow transitionsand existence of hydraulic jump. For a flow through abrupt bed ascension, 3) The flow afterascention is devided into four regions, that is, potential core region, mixing region, developingregion and wall shear layer. The flow of mixing region is similar to the two-dimensional wake.4) The normalized distribution of bed shear stresses at up-stream does not depend on the flowconditions.