Abstract
In 2016, a new criterion called Omega vortex identification was proposed by Liu et al., which has many advantages according to several studies. However, all the existing vortex identification methods are just a scalar and they are contaminated by shear. For the first time in history, a new vortex vector with both local rotation axis and rotation strength - called Liutex (with no shear) was introduced by Liu et al. in 2018. In this study, we load data directly from Liutex vector (Lx, Ly, Lz) instead of velocity (u, v, w). Moreover, proper orthogonal decomposition (POD) method is applied to analyze the coherent structure of the first eighth POD modes in the wake of micro vortex generator at Ma = 2.5 and Reθ = 5760 by using Liutex. Pairing of POD modes is clearly found, which is the sign of Kevin-Helmholtz instability. The observation of the mode paring strongly supports the new mechanism of MVG for reduction of flow separation, which is the interaction between the shock and the spanwise vortex rings generated by K-H instability.
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References
C. Liu, Y. Wang, Y. Yang, et al., New omega vortex identification method. Sci. China Phys. Mech. Astron. 59(8), 684711 (2016)
C. Liu, Y. Gao, S. Tian, et al., Rortex-a new vortex vector definition and vorticity tensor and vector decompositions. Phys. Fluids 30(3), 035103 (2018)
Y. Gao, Y. Yu, J. Liu, C. Liu, Explicit expressions for Rortex tensor and velocity gradient tensor decomposition. Phys. Fluids 31(8), 081704 (2019)
Y. Gao, C. Liu, Rortex based velocity gradient tensor decomposition. Phys. Fluids 31(1), 011704 (2019)
C. Liu, Y. Gao, X. Dong, et al., Third generation of vortex identification methods: Omega and liutex/rortex based systems. J. Hydrodynam. 31, 205 (2019)
M. Love, Probabifity Theory (Van Nostrand, Princeton, NJ, 1955)
L.T. Jolliffe, Principle Component Analysis (Springer-Verlag, New York, 1986)
R.C. Gonzalez, P.A. Wintz, Digital Image Processing (Addison-Wesley, Reading, MA, 1987)
I.T. Jolliffe, Principal Component Analysis (Springer, New York, 1986)
Y.C. Liang, W.Z. Lin, H.P. Lee, S.P. Lim, K.H. Lee, H. Sun, Proper orthogonal decomposition and its applications, part II: Model reduction for MEMS dynamical analysis. J. Sound Vib. 256, 515–532 (2002)
Y.C. Liang, H.P. Lee, S.P. Lim, W.Z. Lin, K.H. Lee, C.G. Wu, Proper orthogonal decomposition and its applications, part I: Theory. J. Sound Vib. 252, 527–544 (2002)
G. Kerschen, J.C. Golinval, A.F. Vakakis, L.A. Bergman, The method of proper orthogonal decomposition for dynamical characterization and order reduction of mechanical systems: an overview. Nonlinear Dyn. 41, 147–170 (2005)
Z. Sun, F.F.J. Schrijer, F. Scarano, B.W.V. Oudheusden, Decay of the supersonic turbulent wakes from micro-ramps. Phys. Fluids 26(2), 389–420 (2014)
H. Babinsky, Y. Li, C.W. Pitt Ford, Microramp control of supersonic oblique shock-wave/boundary-layer interactions. AIAA J. 47, 668–675 (2009)
Q. Li, P. Lu, C. Liu, A. Pierce, F. Lu, Numerical discovery and experimental validation of vortex ring generation by microramp vortex generator, in The 28th International Symposium on Shock Waves, (Springer, Berlin, Heidelberg, 2012), pp. 403–408
K. Taira, Proper orthogonal decomposition in fluid flow analysis: 1. Introduction. J. Japan Soc. Fluid Mech. (Nagare) 30, 115–123 (2011)
J.N. Kutz, S.L. Brunton, B.W. Brunton, J.L. Proctor, Dynamic mode decomposition: Data-driven modeling of complex systems. SIAM 15(1), 142–161 (2016)
Y. Wang, Y. Gao, J. Liu, C. Liu, Explicit formula for the Liutex vector and physical meaning of vorticity based on the Liutex-shear decomposition. J. Hydrodynam. 31(3), 464–474 (2019)
C. Liu, Q. Li, Y. Yan, Y. Yan, G. Yang, X. Dong, High order large eddy simulation for shock-boundary layer interaction control by a micro-ramp vortex generation, in Frontier in Aerospace Science, vol. 2, (2018)
Acknowledgments
The authors are grateful to TACC (Texas Advanced Computation Center) for providing CPU hours to this research project. The computation is performed by using MPI code “LESUTA” which was developed by Drs. Qin Li and Chaoqun Liu.
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Trieu, X.M., Yan, Y., Liu, C. (2021). Liutex and Proper Orthogonal Decomposition for Coherence Structure in the Wake of Micro Vortex Generator. In: Liu, C., Wang, Y. (eds) Liutex and Third Generation of Vortex Definition and Identification. Springer, Cham. https://doi.org/10.1007/978-3-030-70217-5_14
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DOI: https://doi.org/10.1007/978-3-030-70217-5_14
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