Author(s): Yang; Wonjun; Choi; Sung-Uk
Keywords: Turbulent flow; Submerged vegetation; Wide open-channel flow; Mixing layer; Kelvin-Helmholtz vortex
Abstract: Recent numerical simulations by Kang and Choi (2007) reported a local flow acceleration near the sidewall in a wide open-channel flow over submerged vegetation. Motivated by this, laboratory experiments are carried out in a flume whose width to depth ratio is 6. Flexible model vegetation made with polyethylene film is planted on the bottom. LDA is used for the measurement of fluctuating velocity. The mean flow profile revealed that velocity maximum mainly occurs near the sidewall. This is due to the action of the secondary currents, originally, the bottom vortex made bigger by the vegetation drag. The impact of the secondary currents on the turbulence structures is also studied. However, it is found that the mixing layer analogy can be applied to the flow over the whole section. In addition, the impacts of the secondary currents on the mixing layer and Kelvin-Helmholtz vortex are examined and discussed.