Turbulent structure in open-channel flows

English translation of the Japanese dissertation of Iehisa Nezu. Turbulent transport of momentum, heat and mass dominates many of the fluid flows found in physics, engineering and the environmental sciences. Intensive research on the dynamics of the wall turbulence in boundary layer, pipe or channel, especially in an air flow, has been performed by many investigators in the last twenty years. On the other hand, in hydraulics or river mechanics, we are rather concerned about the dynamics of turbulent open-channel water flow since it dominates the turbulent friction law, turbulent diffusion problem, sediment transport in the river field, the flow characteristics near the hydraulic structures and so on. Turbulence measurements in water flow were, however, begun only eight years ago with the development of hot-film anemometers. The detailed investigations on turbulent structure in open-channel flows are still very insufficient, compared with those of air flows in boundary layer or pipe.