力学所Seminar 788
主题：ROTATION DYNAMICS OF ANISOTROPIC PARTICLES IN TURBULENT FLOW
报告人：倪 睿 博士 (耶鲁大学机械工程系)
时间：2013年12月19日（周四)13:30
地点：延长校区应用数学和力学所会议室
主办部门：理学院力学所

Abstract:The motion of the fluid particles in turbulence is fundamental to important transport processes, including mixing of passive scalars and the dispersion of contaminants. A Lagrangian viewpoint following the motion of infinitesimal material fluid elements is conceptually natural and practically useful for studies or applications when transport or aggregation of particulates in turbulence is important.

The fast advances in imaging technology in recent 10 years have made it possible to obtain time-resolved dynamics of particles in turbulence using high-speed stereoscopic imaging. Most previous studies focused on the spherical particles, but the dynamics of anisotropic particles in turbulent fluid flows is central to understanding many applications ranging from cellulose fibers used in paper making to ice crystals in clouds to locomotion of many microorganisms. 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.