Acknowledgment

This work has absorbed very valuable comments on its first draft by Professors Hui-Yang Ma, Chui-Jie Wu, Xi-Yun Lu, De-Jun Sun, Wei-Dong Su, Yue Yang, Doctors Yan-Tao Yang, Feng Mao, Jin-Yang Zhu, Luo-Qin Liu, and Doctoral Candidates Shu-Fan Zou, An-Kang Gao, and Lin-Lin Kang, to whom I am sincerely grateful. But the author is solely responsible for the content and point of view of this communication.

References

[1] H. J. Lugt, in Recent Developments in Theoretical and Experimental Fluid Dynamics, edited by U. Müller, K. G. Roesner, and B. Schmidt (Springer-Verlag, Berlin, 1979), pp. 309-321. Google Scholar http://scholar.google.com/scholar_lookup?title=H. J. Lugt, in Recent Developments in Theoretical and Experimental Fluid Dynamics, edited by U. Müller, K. G. Roesner, and B. Schmidt (Springer-Verlag, Berlin, 1979), pp. 309-321&

[2] H. J. Lugt, Vortex Flow in Nature and Technology (Wiley-Interscience, New York, 1983). Google Scholar http://scholar.google.com/scholar_lookup?title=H. J. Lugt, Vortex Flow in Nature and Technology (Wiley-Interscience, New York, 1983)&

[3] J. C. Wu, Elements of Vorticity Aerodynamics (Tsinghua University Press, Beijing, 2005). Google Scholar http://scholar.google.com/scholar_lookup?title=J. C. Wu, Elements of Vorticity Aerodynamics (Tsinghua University Press, Beijing, 2005)&

[4] H. Helmholtz, J. Reine Angew. Math. 55, 25 (1858). Google Scholar http://scholar.google.com/scholar_lookup?title=H. Helmholtz, J. Reine Angew. Math. 55, 25 (1858)&

[5] C. Truesdell, The Kinematics of Vorticity (Indiana University Press, Bloomington, 1954), p. 105. Google Scholar http://scholar.google.com/scholar_lookup?title=C. Truesdell, The Kinematics of Vorticity (Indiana University Press, Bloomington, 1954), p. 105&

[6] H. Lamb, Hydrodynamics (Dover, New York, 1932), p. 202. Google Scholar http://scholar.google.com/scholar_lookup?title=H. Lamb, Hydrodynamics (Dover, New York, 1932), p. 202&

[7] P. G. Saffman, Vortex Dynamics (Cambridge University Press, Cambridge, 1992), p. 10. Google Scholar http://scholar.google.com/scholar_lookup?title=P. G. Saffman, Vortex Dynamics (Cambridge University Press, Cambridge, 1992), p. 10&

[8] M. J. Lighthill, in Laminar Boundary Layers, edited by L. Rosenhead (Oxford University Press, Oxford, 1963), pp. 46-113. Google Scholar http://scholar.google.com/scholar_lookup?title=M. J. Lighthill, in Laminar Boundary Layers, edited by L. Rosenhead (Oxford University Press, Oxford, 1963), pp. 46-113&

[9] Hicks W. M.. Philos. Trans. R. Soc. London, 1885, 176: 725 CrossRef Google Scholar http://scholar.google.com/scholar_lookup?author=Hicks W. M.&publication_year=1885&journal=Philos. Trans. R. Soc. London&volume=176&pages=725

[10] J. Z. Wu, H. Y. Ma, and M. D. Zhou, Vorticity and Vortex Dynamics (Springer, Berlin, 2006), p. 262. Google Scholar http://scholar.google.com/scholar_lookup?title=J. Z. Wu, H. Y. Ma, and M. D. Zhou, Vorticity and Vortex Dynamics (Springer, Berlin, 2006), p. 262&

[11] She Z. S., Jackson E., Orszag S. A.. Nature, 1990, 344: 226 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=She Z. S.&author=Jackson E.&author=Orszag S. A.&publication_year=1990&journal=Nature&volume=344&pages=226

[12] G. K. Batchelor, An Introduction to Fluid Dynamics (Cambridge University Press, Cambridge, 1967). Google Scholar http://scholar.google.com/scholar_lookup?title=G. K. Batchelor, An Introduction to Fluid Dynamics (Cambridge University Press, Cambridge, 1967)&

[13] L. Prandtl, in Tragflügeltheorie. I. Mitteilung: Nachrichten von der Gesellschaft der Wissenschaften zu G?ttingen, Mathematisch-Physikalische Klasse (1918), pp. 451-477. Google Scholar http://scholar.google.com/scholar_lookup?title=L. Prandtl, in Tragflügeltheorie. I. Mitteilung: Nachrichten von der Gesellschaft der Wissenschaften zu G?ttingen, Mathematisch-Physikalische Klasse (1918), pp. 451-477&

[14] J. Lighthill, in Twentieth Century Physics, vol. II, edited by L. M. Brown, A. Pais, and B. Pippard (AIP Press, Woodbury, 1995), pp. 795-912. Google Scholar http://scholar.google.com/scholar_lookup?title=J. Lighthill, in Twentieth Century Physics, vol. II, edited by L. M. Brown, A. Pais, and B. Pippard (AIP Press, Woodbury, 1995), pp. 795-912&

[15] Betz A.. Naturwissenschaften, 1950, 37: 193 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Betz A.&publication_year=1950&journal=Naturwissenschaften&volume=37&pages=193

[16] Moore D. W., Saffman P. G.. Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci., 1972, 272: 403 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Moore D. W.&author=Saffman P. G.&publication_year=1972&journal=Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci.&volume=272&pages=403

[17] Batchelor G. K.. J. Fluid Mech., 1964, 20: 645 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Batchelor G. K.&publication_year=1964&journal=J. Fluid Mech.&volume=20&pages=645

[18] J. Z. Wu, H. Y. Ma, and M. D. Zhou, Vortical Flows (Springer, Berlin, 2015). Google Scholar http://scholar.google.com/scholar_lookup?title=J. Z. Wu, H. Y. Ma, and M. D. Zhou, Vortical Flows (Springer, Berlin, 2015)&

[19] B. P. Epps, in 55th AIAA Aerospace Sciences Meeting, Grapevine, 2017. Google Scholar http://scholar.google.com/scholar_lookup?title=B. P. Epps, in 55th AIAA Aerospace Sciences Meeting, Grapevine, 2017&

[20] Küchemann D.. J. Fluid Mech., 1965, 21: 1 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Küchemann D.&publication_year=1965&journal=J. Fluid Mech.&volume=21&pages=1

[21] E. A. Müller, and F. Obermeier, in Vortex Motion, Proceedings of the IUTAM Symposium on Fundamental Aspects of Vortex Motion, Tokyo, Japan, 31 August-4 September 1987, edited by H. Hasimoto, and T. Kambe (North-Holland, Amsterdam, 1988), pp. 43-51. Google Scholar http://scholar.google.com/scholar_lookup?title=E. A. Müller, and F. Obermeier, in Vortex Motion, Proceedings of the IUTAM Symposium on Fundamental Aspects of Vortex Motion, Tokyo, Japan, 31 August-4 September 1987, edited by H. Hasimoto, and T. Kambe (North-Holland, Amsterdam, 1988), pp. 43-51&

[22] Moffatt H. K., Kida S., Ohkitani K.. J. Fluid Mech., 1994, 259: 241 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Moffatt H. K.&author=Kida S.&author=Ohkitani K.&publication_year=1994&journal=J. Fluid Mech.&volume=259&pages=241

[23] Yang Y., Pullin D. I.. J. Fluid Mech., 2011, 685: 146 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Yang Y.&author=Pullin D. I.&publication_year=2011&journal=J. Fluid Mech.&volume=685&pages=146

[24] Zhao Y., Yang Y., Chen S.. J. Fluid Mech., 2016, 793: 840 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Zhao Y.&author=Yang Y.&author=Chen S.&publication_year=2016&journal=J. Fluid Mech.&volume=793&pages=840

[25] Zhao Y., Yang Y., Chen S.. J. Fluid Mech., 2016, 802: R4 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Zhao Y.&author=Yang Y.&author=Chen S.&publication_year=2016&journal=J. Fluid Mech.&volume=802&pages=R4

[26] J. Z. Wu, and J. M. Wu, Adv. Appl. Mech. 32, 119 (1996). Google Scholar http://scholar.google.com/scholar_lookup?title=J. Z. Wu, and J. M. Wu, Adv. Appl. Mech. 32, 119 (1996)&

[27] Wu J. Z., Wu J. M.. Theor. Comp. Fluid Dyn., 1998, 10: 459 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Wu J. Z.&author=Wu J. M.&publication_year=1998&journal=Theor. Comp. Fluid Dyn.&volume=10&pages=459

[28] Wu J. Z., Yang Y. T., Luo Y. B., Pozrikidis C.. J. Fluid Mech., 2005, 541: 371 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Wu J. Z.&author=Yang Y. T.&author=Luo Y. B.&author=Pozrikidis C.&publication_year=2005&journal=J. Fluid Mech.&volume=541&pages=371

[29] Y. Chen, Theoretical and Numerical Study on Vorticity Dynamics of Flow with Deformable Boundary. Dissertation for the Doctoral Degree (Fudan University, Shanghai, 2017). Google Scholar http://scholar.google.com/scholar_lookup?title=Y. Chen, Theoretical and Numerical Study on Vorticity Dynamics of Flow with Deformable Boundary. Dissertation for the Doctoral Degree (Fudan University, Shanghai, 2017)&

[30] Zhao H., Wu J. Z., Luo J. S.. Fluid Dyn. Res., 2004, 34: 175 CrossRef ADS Google Scholar http://scholar.google.com/scholar_lookup?author=Zhao H.&author=Wu J. Z.&author=Luo J. S.&publication_year=2004&journal=Fluid Dyn. Res.&volume=34&pages=175