PATTERN CHANGE OF WATER SURFACE VARIATION OF STRIP ROUGHNESS TURBULENCE IN SHALLOW WATER CONDITIONS BY USING IMAGE ANALYSIS TECHNIQUES

Abstract

 In shallow water conditions, open-channel flows are subject to the influence of channel bottom roughness because the boundary layer or vortices generated at the bottom interact with water surface. Such an influence become more pronounced when the bottom is composed of discrete roughness such as a strip roughness. In the present study, water surface variations were investigated experimentally by varying the water depth relative to the roughness height. Although the water surface is kept almost horizontal for a relatively large depth of water, it tends to show significant differences with decrease of water depth. As an example, the water surface exhibits three dimensional topographical features with various arrangement of lumps depending on hydraulic conditions. Moreover, water surface begins to oscillate quite periodically with a hydraulic jump under specific hydraulic conditions. A new image analysis technique was developed to capture such surface flow features.