关于旋涡定义的思考

针对旋涡定义这个长期未解决的难题,在分析历史上提出的几种思路的基础上,本文提出:定义旋涡的总目标,应当体现其管状运动形态,并与其作为流体运动肌腱的动力学功能有机结合;该定义应能以统一的方式覆盖经典涡动力学业已成熟的结果,并且指引对湍流中复杂涡状结构及其相互作用的识别。据此,本文根据涡量场演化的已知规律,提出了旋涡的一个动力学定义,作为继续深化讨论的参考。同时提出,人们针对湍流结构研究构造的各种涡判据,虽然对湍流涡状结构的可视化起了重要作用,但因其难以遵循管式涡量场的因果演化而无法取代完备的涡定义。相比之下,近十年来形成的涡量面理论,有望在未来发展中使旋涡的定义和检验问题回归涡量动力学的自然规律。

Thoughts on vortex definition

Aiming at the long unsolved issue of vortex definition,this article reviewed critically those historically appeared definitions,and thereby proposes that the general goal of vortex definition should reflect an inherent combination of the solenoidal nature of vortices in kinematics and their role as the sinews and muscles of fluid motion in dynamics.The definition should,in a unified manner,cover all mature achievements of classic vortex dynamics and guide the identification of complex vortical structures and interactions in turbulence.Thus,on the basis of the known evolution laws of vorticity field,we propose a dynamic definition of vortices as a reference of further discussion.Although various "vortex criteria"constructed for visualizing turbulent structures have played important role in one’s understanding,they cannot replace a complete vortex definition since they do not follow the causal evolution rules of the solenoidal vorticity field.In contrast,it is expected that the vorticity-surface theory formed in the past decade will,in its future development,be able to bring the definition of vortex and its testing back to the natural laws of vorticity dynamics.