Simulation Based Study of Boundary-Layer Flows at Wave Surfaces

报告题目：Simulation Based Study of Boundary-Layer Flows at Wave Surfaces 
报告人：Shen Lian 教授 
单位：University of Minnesota，Department of Mechanical Engineering　
报告时间：2013年10月18日(周五)14:30 
报告地点：工程学院力一楼239会议室 

报告人简介： 
Dr. Lian Shen obtained his bachelor’s degree in mechanics from University of Science and Technology of China in 1993 and his doctoral degree in fluid mechanics from Massachusetts Institute of Technology in 2001.  In 2004, he joined the faculty of civil engineering at Johns Hopkins University as assistant professor.  He currently holds the position of Benjamin Mayhugh Associate Professor in Department of Mechanical Engineering at University of Minnesota.  Dr. Shen’s research interests include turbulence simulation and modeling, boundary-layer flows, free-surface and multi-fluids flows, and fluid mechanics in energy and environment applications.  He has participated in many research projects of US National Science Foundation and Office of Naval Research, some of which involve large field campaigns and Dr. Shen has played a leading role in the theoretical and computational efforts of these projects.  He has published extensively in top journals in fluid mechanics. In addition, Dr. Shen has received a number of awards including the Martin A.  Abkowitz Fellowship, the Office of Naval Research Young Investigator Award, and the T. Francis Ogilvie Lectureship.

报告摘要：
The mechanism of turbulence at wavy boundaries is important to many applications.  Examples include turbulence transport of momentum, mass, and heat at gas-liquid interfaces in many industrial processes involving multi- fluids flows, biomimetics of fish swimming using body waving motion for drag reduction and efficient propulsion, and environmental flows involving undulatory terrains and water surface waves.  In this work, a systematic, simulation-based study was carried out to understand the fundamental mechanism of turbulence boundary-layer flows at wave surfaces.  Direct numerical simulation was first performed for turbulent flows above and under monochromatic waves to elucidate the details of the flow structure; large- eddy simulation with a new dynamic wave-surface roughness model was then performed for flows over irregular waves with broadband spectra to quantify  the form drag and mechanical energy flux at the surface.  Extensive comparison of the simulation results with measurement data was performed, and good agreement has been obtained.  Substantial new understanding of the flow physics has been gained in terms of vortex dynamics, Reynolds stress  variation, and kinetic energy budget.  As an application, atmospheric boundary layers over ocean waves with wind turbine model were simulated for the study of offshore wind energy.  It is found that wind-waves at different development stages possess different sea-surface roughness and have an appreciable effect on wind profile and the energy extraction rate of the turbines.  In the presence of swells, which are large waves generated by distant storms, swell-to-wind momentum and energy transfer can substantially affect the wind field to cause fluctuations in and change the mean of wind power.

Shen Lian 教授计划明年招收多位学生，感兴趣明尼苏达大学的学生欢迎参加，报告后可与沈老师交流。