Stretching and shearing contamination analysis for Liutex and other vortex identification methods

Advances in Aerodynamics

Charles Nottage¹  Oscar Alvarez¹  Pushpa Shrestha¹  Yifei Yu¹  Chaoqun Liu¹ 

[1] Department of Mathematics, The University of Texas at Arlington, 76019, Arlington, TX, USA;

关键词: Liutex;    Vorticity;    Vortex;    Omega method;    Transition flow;    Velocity gradient tensor;    Principal coordinate;    Principal tensor;    Liutex tensor decomposition;   

DOI  :  10.1186/s42774-020-00060-9

来源: Springer

【 摘 要 】

The newly developed vortex-identification method, Liutex, has provided a new systematic description of the local fluid rotation, which includes scalar, vector, and tensor forms. However, the advantages of Liutex over the other widely used vortex-identification methods such as Q, ∆, λ2, and λci have not been realized. These traditional methods count on shearing and stretching as a part of vortex strength. But, in the real flow, shearing and stretching do not contribute to fluid rotation. In this paper, the decomposition of the velocity gradient tensor is conducted in the Principal Coordinate for uniqueness. Then the contamination effects of stretching and shearing of the traditional methods are investigated and compared with the Liutex method in terms of mathematical analysis and numerical calculations. The results show that the Liutex method is the only method that is not affected by either stretching or shear, as it represents only the local fluid rigid rotation. These results provide supporting evidence that Liutex is the superior method over others.

【 授权许可】

CC BY