MIXING STRUCTURE AND FLOW EVOLUTION RESULTING FROM VARIATION IN THE DENSITY OF RIPARIAN VEGETATION ALONG THE BANKS OF A MAIN CHANNEL IN A COMPOUND CHANNEL

摘要

This research elucidated the process of change in mixing mechanisms associated with change in vegetation density, as well as the process of change directly upstream and downstream from the vegetation, and considered flow field transition distance. It was found that immediately downstream from the vegetation, the abrupt inflow of the floodchannel flow into the main channel resulted in extensive horizontal mixing that exceeded the mixing between flows inside and outside of the vegetation. Another important characteristic was that the vigorous mixing immediately downstream from the vegetation is diffused by large-scale horizontal eddies. As with cases of density that is greater downstream, the process of mixing development is one in which the development of large-scale eddies changes the main channel layer's velocity distribution, resulting in vertical mixing.