RESEARCH ON THE GENERATION OF LONGITUDINAL VORTICES AND ITS CONTROL IN TURBULENT SHEAR FLOWS

点击翻译按钮获取中文摘要

To research this project, the next three groups were organized,i.e.1.Coherent structure, 2.Secondary flows and 3.Longitudinal vortices in complicated channels under the umbrella of this project. Many co-operative researchers who were intersted in this project joined the three groups besides the investigators of this project. Forums were held three or four times every year to get mutual understanding of the results and to focus problems occurring in the research on the aim of this project through lively discussions by the participants of the forum. The following are the research results of this project:1. Coherent structure: Coherent structure is affected by initial and boundary conditions and is related directly to the drag reduction and the delay of transition. The relation between streaky structure and longitudinal vortices was researched in various types of flow.2. Secondary flows: Momentum transport to the spanwise direction plays an important role in the generation of steady secondary flow. It is caused by additional longitudinal vortices, uneven Reynolds stress, centrifugal instability and instability of separation shear layer in adverse pressure gradient.3. Longitudinal vortices in complicated channels: Contribution and control of longitudinal vortices was researched on mass transport in a wavy channel, local erosion in a river, drag reduction caused by uneven injection of dense polymer solution in a turbulent pipe flow and generation of particle clusters in a fluidized bed. Structure of longitudinal vortices was also researched in the wake of a body and falling water.The research results of this project were published in 25 papers in the report of this project and in 66 papers in various journals and were presented in 91 presentations at many meetings or conferences.