Structure and Dynamics of Turbulent Elementary Vortices

在对初等涡旋基本性质的研究中，定量地阐明了初等涡旋物理特性的空间分布及其与雷诺数的依赖关系，表明初等涡旋在较大的雷诺数下仍然具有重要的动力学意义。本文提出了一种自动追踪涡旋的方法，以寻找涡旋的反平行路径，从而使流体线和表面呈指数级扩展。流体的可压缩性可以诱导涡旋波并抑制涡旋的生长。在MHD湍流中发现了对流涡旋与磁场相互作用的一种新的发电机现象。在库埃特湍流中发现了伴随初级涡的产生和破裂的不稳定周期运动。在基本涡的基本动力学特性研究中，研究了大尺度相干垂直结构与湍流场的相互作用。前者在涡表面产生细尺度涡并缠绕，在相干涡内部产生轴对称弯曲涡。另一方面，初级涡产生的涡环增强了涡核外围的能量耗散。在泊泽维尔湍流中，在外层和在内层中都观察到纵向涡旋和条纹结构。

In the study of the basic properties of the elementary vortices, the spatial distribution and the Reynolds number dependence of their physical characteristics have been clarified quantitatively, suggesting that the elementary vortices may keep their dynamical importance at larger Reynolds numbers. An automatic chasing scheme of vortices has been developed to find the anti-parallel approach of vortices, which stretch the fluia lines and surfaces exponentially in time. The compressibility of fluids has been shown to induce vortex waves and to suppress the vortex growth. A new dynamo phenomenon by interactions between convection vortices and magnetic fields has been discovered in MHD turbulence. unstable periodic motions accompanying the generation and breakdown of the elementary vortices has been found in Couette turbulence. In the study of basic dynamical properties of the elementary vortices, the interaction of large-scale coherent vertical structures and turbulent field has been investigated with or without the axial flow in the coherent vortices. In the former case, fine scale vortices are generated and wrapped around the vortex surface, and axi-symmetric bending vortices are generated inside the coherent vortex. In the latter, on the other hand, vortex rings produced from the elementary vortices enhance the energy dissipation at the periphery of the vortex core. In a Poiseuille turbulence, longitudinal Vortex and streak structures have been observed in the outer layer like as in the inner layer.