複断面開水路流の三次元乱流構造

抄録

An investigation on three-dimensional turbulent structure accompanied with turbulence-driven secondary currents in compound open-channel flows is very important in basic hydraulics as well as river engineering to elucidate the friction law of the flow and sediment transport. In this study, accurate measurements in fully developed compound open-channel flows were conducted by making use of fiber-optic laser Doppler Anemometer (FLDA) and X-type hot-film anemometer. Strong inclined upflow which is associated with a pair of longitudinal vortices is generated in a junction region between a main channel and a flood plain. Primary mean velocity is directly influenced by the secondary currents. The structures of turbulence intensities and Reynolds stresses are observed in detail. The contribution of secondary currents to spanwise momentum transport from the main channel to the flood plain is found to be very large.