题 目：Rotation Dynamics of Anisotropic Particles in Turbulent Flow
报告人：倪睿博士（Yale University , USA）
In both physical and biological science, we are often concerned with the dynamics of the small particles, which are suspended and carried about by the motion of the fluid. The first complete mathematical treatment of the problem has been given by Einstein in 1905, who considered the case of spherical particles and gave a simple formula for the increase in the viscosity. Jeffery extended this work to characterize the rotation of anisotropic particles in a simple linear shear flow in 1922, which is usually referred to as Jeffery orbits. Previous experiments showed many fascinating dynamics of anisotropic particles even in simple flows. But flow in nature is usually complicated and turbulent. The fast advances in imaging technology have made it possible to obtain time-resolved rotation dynamics of anisotropic particles in turbulence using high-speed stereoscopic imaging. We have developed a general methodology to experimentally measure the time-resolved orientation and solid body rotation rate of anisotropic particles with arbitrary aspect ratio, which are designed and fabricated through 3D printing technology. In order to measure the flow surrounding the anisotropic particles, we built a scanning particle tracking system to measure the velocity of high concentration tracer particles along with the orientation of a small concentration of anisotropic particles. We found that the long axis of the anisotropic particle is preferentially aligned with the direction of the vorticity vector. The reason for that is because both the anisotropic particle and vorticity vector tend to be independently aligned with the largest stretching direction.
倪睿博士2011年博士毕业于香港中文大学物理系，现任耶鲁大学机械工程与材料科学系，卫斯理大学物理系（兼）博士后研究员。主要从事热对流、湍流伸展和涡旋的动力学、以及聚合物与湍流的相互作用的研究；探讨它们在物理海洋学、微流与纳米流体、软物质物理等科研领域以及昆虫群体飞行等生物流体问题上的应用。是国际流体物理领域优秀的青年科学家。至今已发表SCI论文12篇，其中包括3篇Physical Review Letters，3篇Physical Review E.，1篇Applied Physics Letter，以及多篇流体物理领域顶级期刊Journal of Fluid Mechanics, Physics of Fluid 上的论文。参与国家自然科学基金和香港研究资助局的项目研究。现任美国物理学会会员，担任Physical Review Letters, Journal of Fluid Mechanics 等五种国际学术期刊的审稿人。