Author(s): Michio Sanjou; Iehisa Nezu; Sohei Suzuki
Linked Author(s): Michio Sanjou
Keywords: Horizontal vortex; Compound open-channel flow; Trajectory of vortex; ADV and PIV
Abstract: Compound open-channel flows are composed of main-channel and floodplains in natural rivers. Many previous studies pointed out that coherent horizontal vortices appear with a constant spacing in the streamwise direction. These are generated by a shear instability associated with the velocity differences between the main-channel and floodplains in the similar mechanism to coherent vortices in mixing layers. Recently, several highly accurate turbulence measurements have been conducted with laser Doppler anemometer (LDA) and PIV, and they offer very valuable database of observed turbulent structures and coherent vortices. However, most of these studies dealt with fixed measuring zone and thus there remain a lot of uncertainties about streamwise convection of a typical horizontal vortex with a long duration. So, in this study, both of ADV and PIV measurements were conducted. In particular, for the present PIV, a specially designed CMOS camera system was developed, which can be moved with the same speed as the convection velocity of a typical horizontal vortex.