Experimental Study On Coherent Structure Of Turbulent Boundary Layer In Smooth Open-Channel Flow

The coherent structure of turbulent boundary layer is the most important discover and the most interesting problem of turbulence research in the last several decades. In this paper, the new idea simultaneously using the Planar Laser Induced Fluorescence (PLIF) technique and the Acoustic Doppler Velocimeter (ADV) technique is applied to research the coherent structure of turbulent boundary layer.The research works include:1. The flow visualization and concentration field measurement system based on PLIF technique and the ADV automatic measurement and analysis system are established. The adaptive data handling methods are rendered.2. The mean and turbulent characteristics of turbulent boundary layer are studied using the ADV automatic measurement and analysis system for the first time. Distributions of mean velocity, turbulent intensity and skewness factor can be applied to distinguish the flow sub-field.3. The velocity, image and concentration time sequences are simultaneously acquired using PLIF and ADV techniques.The bursting shape, the bursting angle, the bursting height, motion of vortex and so on are researched through the image and concentration time sequences. The PLIF technique is successfully developed to visualize and quantify the coherent structure of turbulent boundary layer.The average bursting period is studied introducing several data handling methods. The relations with bursting frequency and Reynolds number are established and analyzed.4. The relations with coherent structure and sediment movement, coherent structure and bed configuration are analyzed according to previous work. This paper points out that there is inevitable relation between them.