报告摘要：

       The statistical evidence for the existence and properties of coherent structures in wall-bounded turbulent flow is reviewed. It is argued that there are at least three kinds of structures, distinguishable by their correlations and by their propagation velocity. The best known are the buffer-layer streaks of the streamwise velocity, and their associated vortices. They can be described as relatively long-lived dispersive wave packets, and do not extend beyond y+≈80. Similar to them, but larger (Lx>0.5h) and internally turbulent, are the outer streaks. They scale in outer units, and can also be described as permanent and dispersive. Streaks carry most of the kinetic energy at their respective wall distances. Thirdly, there is a self-similar family of shorter cross-stream structures. They are closely coupled to the shear, which tilts them forwards and determines their lifetime. Their conditional flow field can be described as an inclined large-scale ‘roller’ associated with a kink in the streak, and they are responsible for most of the Reynolds stresses. All these structures are essentially independent of the wall, because they exist as both attached and detached eddies in wall-bounded flows, and in wall-less homogeneous shear turbulence.

报告人简介：

   Javier Jimenez现为马德里科技大学航空系教授、西班牙科学院和工程院双院士、斯坦福大学湍流研究中心客座教授。1973年在加州理工学院获博士学位。他在湍流的理论研究和数值模拟、以及CFD数值算法等方面享有国际声誉。在包括Science、Annual Review of Fluid Mechanics、Journal of Fluid Mechanics等流体力学顶级期刊发表论文110余篇，SCI引用6700余次，H-index为39。在包括美国物理学院、欧洲湍流会议委员会、Physics of Fluid等十余个国际学术机构和期刊担任学术兼职。Jimenez教授现仍保有壁湍流大规模DNS的世界记录，所持有的壁湍流DNS数据库完全对外开放，是被其他研究者使用最多的湍流DNS数据库之一。