COHERENT HORIZONTAL VORTICES IN UNSTEADY DEPTH-VARYING COMPOUND OPEN-CHANNEL FLOWS

摘要

Compound open-channel flows are composed of a main-channel and floodplains. From a lot of experimental and numerical studies, it has been found that coherent horizontal vortex appears near the junction, and it promotes the transverse momentum transport between the main-channel and floodplain. However, no database of unsteadiness characteristics of horizontal vortices in rectangular/compound depth-varying open-channel flows is available as yet. So in this study, turbulence measurements were conducted in the time-dependent and depth-varying unsteady compound open-channel flows using a PIV system. As the results, the generation and development processes of horizontal vortices were investigated considering the inflectional instability property. Particularly, it was revealed experimentally that the single eddy structure is changed to the twin eddies structure with an increase of time-dependent water depth.