Image Analysis and LES of Open-Channel Flow with Strip Roughness

River bed is composed of movable material such as sand or grain and small or large scale vortices are generated at the bed, which are generally lifted upward making confliction with water surface. The confliction of vortices against the water surface yields surface ripples making water-surface configuration rather complicated. Although there are a large number of researches on rough bed flows, the interrelationship between flow and water surface has not been clarified so far. In order to investigate fundamental features of flows with rough walls, measurements are made for the flows with strip roughness. A numerical simulation by LES is also performed to compare with the experimental results, showing a reasonable agreement with the experiments.