题 目：Experimental and numerical investigations of Wave-Current Interaction
时 间：2018年11月22日上午9：00
地 点： 土木交通大楼319会议室
主讲人简介：
My name is Xuan Zhang, and I am a PhD from UCL, majoring in fluid mechanics and coastal engineering. After I obtained my Bachelor’s Degree from Hohai University in 2013, I started my PhD studies in UCL, funded by the UCL Dean’s Prize and China Scholarship Council. I have successfully been awarded the PhD degree in October of 2018 and my PhD thesis and my viva were evaluated as very high-standard by the examiners.
My supervisor is Professor Richard Simons, and my PhD project provides an insightful physical study of combined wave-current boundary layers, involving an extensive laboratory study performed in different flumes varying in scale. The originality of my work and the analysis will advance the understanding of boundary layers under the combined effects from waves and a turbulent current. I have also developed a CFD model using the package Ansys Fluent to numerically describe wave-current interaction. I presented my project at the 11th UK Young Coastal Scientists and Engineers Conference where I was awarded the second prize. Knowledge obtained from the project will provide some guidance for design of marine energy devices. For example, this can provide a better design of tidal turbines, provide an insight into improving the energy cost, and propose a framework of improving current standards.
讲座简介：
The hydrodynamics of coastal zones are dominated by two important factors: gravity waves and currents. The waves are usually generated by the wind, while the currents can be generated by the waves, density variations, tides etc. With the development in marine energy exploitation, the interaction between surface gravity waves and a tidal current (WCI) is highly significant for engineers concerned with hydrodynamics in the near-shore region. Renewable energy devices such as tidal turbines, as well as other forms of coastal structure, are located in a complex environment involving ocean waves and a tidal current. Evaluation of coastal erosion, design of harbour structures, pipelines and tidal turbines, and dispersal of pollutants are examples which require a clear understanding of wave-current interaction.
Physically, it is complicated to determine how ocean waves interact with the turbulent currents because of many complex physical processes involving various temporal and spatial scales. The complicated physical processes have been analysed using analytical approximations, experiments and numerical simulations. Previous studies were mainly focused on changes in wave kinematics and wave attenuation caused by bottom friction under the combined condition. Existing studies have identified the non-linear characteristics of WCI, with experimental studies describing the phenomena and semi-empirical models attempting to quantify them. This presentation presents some progress on investigating changes of velocity distributions and Reynolds stresses in combined wave-current boundary layers. A numerical CFD model has also been developed to describe waves propagating with a turbulent current. Results were compared with experimental data from Kemp and Simons (1982), and good agreements found.
