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Explicit formula for the Liutex vector and physical meaning of vorticity based on the Liutex-Shear decomposition

  • Yi-qian Wang
  • Yi-sheng Gao
  • Jian-ming Liu
  • Chaoqun LiuEmail author
Article
  • 37 Downloads

Abstract

In the present study, the physical meaning of vorticity is revisited based on the Liutex-Shear (RS) decomposition proposed by Liu et al. in the framework of Liutex (previously called Rortex), a vortex vector field with information of both rotation axis and swirling strength (Liu et al. 2018). It is demonstrated that the vorticity in the direction of rotational axis is twice the spatial mean angular velocity in the small neighborhood around the considered point while the imaginary part of the complex eigenvalue (λci) of the velocity gradient tensor (if exist) is the pseudo-time average angular velocity of a trajectory moving circularly or spirally around the axis. In addition, an explicit expression of the Liutex vector in terms of the eigenvalues and eigenvectors of velocity gradient is obtained for the first time from above understanding, which can further, though mildly, accelerate the calculation and give more physical comprehension of the Liutex vector.

Key words

Vorticity Liutex Liutex-Shear decomposition explicit formula of Liutex 

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Notes

Acknowledgements

The work is partly supported by China Post-Doctoral Science Foundation (Grant No. 2017M610876), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant Nos.18KJA110001), and the Visiting Scholar Scholarship of the China Scholarship Council (Grant No. 201808320079). This work is partly accomplished by using code DNSUTA developed by Dr. Chaoqun Liu at the University of Texas at Arlington.

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Copyright information

© China Ship Scientific Research Center 2019

Authors and Affiliations

  • Yi-qian Wang
    • 1
  • Yi-sheng Gao
    • 2
  • Jian-ming Liu
    • 3
  • Chaoqun Liu
    • 2
    Email author
  1. 1.School of Aerospace EngineeringTsinghua UniversityBeijingChina
  2. 2.Department of MathematicsUniversity of Texas at ArlingtonArlingtonUSA
  3. 3.School of Mathematics and StatisticsJiangsu Normal UniversityXuzhouChina

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