Author(s): Iehisa Nezu; Kazunori Noguchi; Tomohiro Nakajima; Tetsuro Akimoto
Linked Author(s): Iehisa Nezu
Keywords: No Keywords
Abstract: Sediment particles are lifted-up and transported by the coherent eddies in actual rivers. Especially in the flow over sand dunes, the sediment particles are mainly lifted-up by the kolk-boil vortex, which is an upward flow from the reattachment point toward the free surface. 3-D structure of the kolk-boil vortex over dune is too complicated to measure experimentally, and therefore, the structure of kolk-boil vortex has been examined mainly in the x-y (streamwise-vertical) plane in many previous experimental studies. In this study, two kinds of main experiments are conducted, i.e., one is the case of clear-water flow, and the other is the case of sediment-laden flow. As the results, the low-speed region of boils was measured on both x-z (streamwise-spanwise) horizontal viewpoints by using PIV system. Consequently, the boil region was convected to the free surface keeping the state of low-speed fluid, and a lot of sediment particles are lifted-up in the low-speed region of boils.
Year: 2009