Investigation on coherent structures in partly vegetated open-channel flows with PIV

Abstract

Various anemometers, such as a pitot tube, hot-film anemometer and laser Doppler anemometer, have been used to measure the turbulent structures of closed duct flows, boundary layers, open-channel flows and so on. However, it is difficult to investigate of coherent structures such as surface vortices in open-channel flows. In this study, the turbulence measurements of open-channel flows with the vegetated zone at the half channel width were conducted by making use of a Particle Image Velocimetry(PIV). It was found that the horizontal vortices near the free surface are generated by the shear instability which increases with an increase of the vegetation density and also that the horizontal vortices were affected strongly by the vegetation density.