開水路断面変化部における流れの水理特性について(1) ―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-ascension or depression.Characteristics of flow transition, separation region and velocity distribution near the positionof bed-variation are investigated. The measurements of separation region were made by thetechnique of flow visualization with potassium perinanganate tracer, and velocity measurementsby a hot-film flowineter of constant-temperature operation.Experimental results obtained are as follows; 1) The transition of flow can not always bedescribed by a simplified method of momentum analysis. 2) The length and the height ofseparation region formed near a bed-ascension or depression depend on many factors suchas the height of bed-variation, up- and

or down-stream depth, Froude number and so on.3) The vertical distribution of mean velocity near the bed-variation can not be approximatedby the logarithmic law, and the energy and momentum coefficients are greater than unity.4) The intensity of turbulence is high, and the maximum rate of turbulence energy dissipa-tion in total energy loss reaches a few tens percent, which is several times of that of twodimensional uniform flow.