Third generation of vortex identification methods:Omega and Liutex/Rortex based systems  

作　　者：Chaoqun Liu Yi-sheng Gao Xiang-rui Dong Yi-qian Wang Jian-ming Liu Yu-ning Zhang Xiao-shu Cai Nan Gui 

机构地区：[1]Department of Mathematics,University of Texas at Arlington,Arlington 76019,Texas,USA [2]College of Energy and Power Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China [3]School of Aerospace Engineering,Tsinghua University,Beijing 100084,China [4]School of Mathematics and Statistics,Jiangsu Normal University,Xuzhou 221116,China [5]Key Laboratory of Condition Monitoring and Control for Power Plant Equipment(Ministry of Education),School of Energy,Power and Mechanical Engineering,North China Electric Power University,Beijing 102206,China [6]Institute of Nuclear and New Energy Technology,Collaborative Innovation Center of Advanced Nuclear Energy Technology,Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education,Tsinghua University,Beijing 100084,China

出　　处：《Journal of Hydrodynamics》2019年第2期205-223,共19页水动力学研究与进展B辑（英文版）

摘　　要：A vortex is intuitively recognized as the rotational/swirling motion of fluids,but a rigorous and universally-accepted definition is still not available.Vorticity tube/filament has been regarded equivalent to a vortex since Helmholtz proposed the concepts of vorticity tube/filament in 1858 and the vorticity-based methods can be categorized as the first generation of vortex identification methods.During the last three decades,a lot of vortex identification methods,including 0,A,and Aci criteria,have been proposed to overcome the problems associated with the vorticity-based methods.Most of these criteria are based on the Cauchy-Stokes decomposition and/or eigenvalues of the velocity gradient tensor and can be considered as the second generation of vortex identification methods.Starting from 2014,the Vortex and Turbulence Research Team at the University of Texas at Arlington(the UTA team)focus on the development of a new generation of vortex identification methods.The first fruit of this effort,a new Omega(/2)vortex identification method,which defined a vortex as a connected region where the vorticity overtakes the deformation,was published in 2016.In 2017 and 2018,a Liutex(previously called Rortex)vector was proposed to provide a mathematical definition of the local rigid rotation part of the fluid motion,including both the local rotational axis and the rotational strength.Liutex/Rortex is a new physical quantity with scalar,vector and tensor forms exactly representing the local rigid rotation of fluids.Meanwhile,a decomposition of the vorticity to a rotational part namely Liutex/Rortex and an anti-symmetric shear part(RS decomposition)was introduced in 2018,and a universal decomposition of the velocity gradient tensor to a rotation part(7?)and a non-rotation part(NR、was also given in 2018 as a counterpart of the traditional Cauchy-Stokes decomposition.Later in early 2019,a Liutex/Rortex based Omega method called Omega-Liutex,which combines the respective advantages of both Liutex/Rortex and Omega methods,was dev

关 键 词：VORTEX DEFINITION VORTEX identification OMEGA Liutex/Rortex direct NUMERICAL simulation TURBULENCE 

分 类 号：O3[理学—力学]