STUDY ON THE STRUCTURE OF LARGE SCALE TURBULENCE BY FLOW VISUALIZING METHOD

During the last ten years coherent characteristics of large scale turbulence in boundarylayers have been made clear. The results of these studies encouraged the authors to study thestructures of large scale turbulence with the intention of applying the result to practical riverengineering.On the other hand, it is suggested that there exist secondary flows in river flows and theyplay an important role in fluvial process. But it has been considered that a secondary flow isone thing and large scale turbulence is another.In this paper, a flow model is proposed, by which generation and development of turbu -lence as well as energy cascade process can be elucidated. Furthermore, it is shown that thesecondary flow is a phase of large scale turbulence in this flow model.Some visual observations about flow patterns around channel bed and a water surface andthe experimental results obtained are shown to confirm the flow model.During the last ten years coherent characteristics of large scale turbulence in boundarylayers have been made clear. The results of these studies encouraged the authors to study thestructures of large scale turbulence with the intention of applying the result to practical riverengineering.On the other hand, it is suggested that there exist secondary flows in river flows and theyplay an important role in fluvial process. But it has been considered that a secondary flow isone thing and large scale turbulence is another.In this paper, a flow model is proposed, by which generation and development of turbu -lence as well as energy cascade process can be elucidated. Furthermore, it is shown that thesecondary flow is a phase of large scale turbulence in this flow model.Some visual observations about flow patterns around channel bed and a water surface andthe experimental results obtained are shown to confirm the flow model