Abstract
The complex vortex structures in the flow around turbine rotor passages, with weak or strong, large or small vortices, interacting with each other, often generate most of aerodynamic loss in turbomachines. Therefore, it is important to identify the vortex structures accurately for the flow field analysis and the aerodynamic performance optimization for turbomachines. In this paper, by using 4 vortex identification methods (the Q criterion, the Ω method, the Liutex method and the Ω-Liutex method), the vortices are identified in turbine rotor passages. In terms of the threshold selection, the results show that the Ω method and the Q-Liutex method are more robust, by which strong and weak vortices can be visualized simultaneously over a wide range of thresholds. As for the display consistency of the vortex identification methods and the streamlines, it is shown that the Liutex method gives results coinciding best with the streamlines in identifying strong vortices, while the Ω-Liutex method gives results the most consistent with the streamlines in identifying weak vortices. As to the relationship among the loss, the vortices and the shear, except for the Q criterion, the other three methods can distinguish the vortical regions from the high shear regions. And the flow losses in turbine rotor passages are often related to high shear zones, while there is a small loss within the core of the vortex. In order to obtain the variation of vortices in the turbine rotor passages at different working points, the Liutex method is applied in 2 cases of a turbine with different angles of attack. The identification results show that the strengths of the tip leakage vortex and the upper passage vortex are weaker and the distance between them is closer at a negative angle of attack. This indicates that the Liutex method is an effective method, and can be used to analyze the vortex structures and their evolution in turbine rotor passages.
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References
Zou Z. P., Wang S. T., Liu H. X. et al. Axial Turbine Aerodynamics for Aero-engines: Flow Analysis and Aerodynamics Design [M]. Singapore: Springer, 2018.
Denton, J. D. Loss mechanisms in turbomachines [J]. Journal of Turbomachinery, 1993, 115: 621–656.
Filippov G. A., Wang Z. Q. The calculation of axial symmetric flow in a turbine stage with small ratio of diameter to blade length [J]. Journal of Moscow Power Institute, 1963, 47: 63–78.
Deich M. E., Zaryakin A. E., Fillipov G. A. et al. Method of increasing the efficiency of turbine stages and shon blades [J]. Teploenergetika, 1960, 2: 18–24.
Zhang W. H., Zou Z. P., Jian Y. Leading-edge redesign of a turbomachinery blade and its effect on aerodynamic performance [J]. Applied Energy, 2012, 93(5): 655–667.
Zou Z. P., Shao F., Li Y. R. et al. Dominant flow structure in the squealer tip gap and its impact on turbine aerodynamic performance [J]. Energy, 2017, Volume 138: 167–184.
Zou Z. P., Liu J. Y., Zhang W. H. et al. Shroud leakage flow models and a multi-dimensional coupling CFD (computational fluid dynamics) method for shrouded turbines [J]. Energy, 2016, 103: 410–429.
Helmholtz H. Überintegrale der hydrodynamischen Gleichungen, welche den Wirbelbewegungen entsprechen [J]. Journal für die reine und angewandte Mathematik, 1858, 55: 25–55.
Brachet M. E., Meneguzzi M., Politano H. et al. The dynamics of freely decaying two-dimensional turbulence [J]. Journal of Fluid Mechanics, 1988, 194: 333–349.
Babiano A., Basdevant C., Legras B. et al. Vorticity and passive-scalar dynamics in two-dimensional turbulence [J]. Journal of Fluid Mechanics, 1987, 183: 379–397.
Robinson S. K., Kline S. J., Spalart P. R. A review of vortex structures and associated coherent motions in turbulent boundary layers [C]. Proc 2nd IUTAM Symposium on Structure of Turbulence and Drag Reduction, Zurich, Switzerland, 1989.
Dong X. R., Dong G. and Liu C. Q. Study on vorticity structure in late flowtransition [J]. Physics of Fluids, 2018, 30(10): 104108.
Dong X. R., Tian S. L., Liu C. Q. Correlation analysis on volume vorticity and vortex in late boundary layer transition [J]. Physics of Fluids, 2018, 30(1): 014105.
Hunt J. C. R., Wray A. A., Moin P. Eddies, streams, and convergence zones in turbulent flows [R]. Center for Turbulent Research Report CTR-S88, 1988, 193–208.
Chong M. S., Perry A. E., Cantwell B. J. A general classification of three-dimensional flow fields [J]. Physics of Fluids, 1990, 2(5): 765–777.
Jeong J., Hussain F. On the identification of a vortices [J]. Journal of Fluid Mechanics, 1995, 332(1): 339–363.
Zhou J., Adrian R., Balachandar S. et al. Mechanisms for generating coherent packets of hairpinvortices in channel flow [J]. Journal of Fluid Mechanics, 1999, 387(10): 353–396.
Liu C. Q., Wang Y. Q., Yang Y. et al. New omega vortex identification method [J]. Science China Physics, Mechanics and Astronomy, 2016, 59(8): 684711.
Zhang Y. N., Liu K. H., Li J. W. et al. Analysis of the vortices in the inner flow of reversible pump turbine with the new omega vortex identification method[J]. Journal of Hydrodynamics, 2018, 30(3): 463–469.
Zhang Y. N., Qiu X., Chen F. P. et al. A selected review of vortex identification methods with applications [J]. Journal of Hydrodynamics, 2018, 30(5): 767–779.
Liu C., Cai X. S. New theory on turbulence generation and structure—DNS and experiment [J]. Science China Physics, Mechanics and Astronomy, 2017, (08): 084731.
Tian S. L., Gao Y. S., Dong X. R. et al. Definitions of vortex vector and vortex [J]. Journal of Fluid Mechanics, 2018, 849: 312–339.
Liu C. Q., Gao Y. S., Tian S. L. et al. Rortex—A new vortex vector definition and vorticity tensor and vector decompositions [J]. Physics of Fluids, 2018, 30(3): 035103.
Wang Y. Q., Gao Y. S., Liu C. Q. Letter: Galilean invariance of Rortex [J]. Physics of Fluids, 2018, 30(11): 111701.
Liu C., Gao Y. S., Dong X. R. et al. Third generation of vortex identification methods: Omega and Liutex/Rortex based systems [J]. Journal of Hydrodynamics, 2019, 31(2): 205–223.
Gao Y. S., Liu C. Q. Rortex and comparison with eigenvalue-based vortex identification criteria [J]. Physics of Fluids, 2018, 30(8): 085107.
Dong X. R., Gao Y. S., Liu C. Q. New Normalized Rortex/Vortex Identification Method [J], Physics of Fluids, 2019, 31(1): 011701.
Liu J. M., Wang Y. Q., Gao Y. S. et al. Galilean invariance of Omega vortex identification method [J]. Journal of Hydrodynamics, 2019, 31(2): 249–255.
Wang Y. Q., Yang Y., Yang G. et al. DNS Study on Vortex and Vorticity in Late Boundary Layer Transition [J]. Communications in Computational Physics, 2017, 22(2): 441–459.
Dong X. R., Wang Y. Q., Chen X. P. et al. Determination of epsilon for Omega vortex identification method [J]. Journal of Hydrodynamics, 2018, 30(4): 541–548.
Wang Y. Q., Gao Y. S., Liu J. M. et al. Explicit formula for the Liutex vector and physical meaning of vorticity based on the Liutex-Shear decomposition [J]. Journal of Hydrodynamics, 2019, 31(3): 464–474.
Acknowledgements
This work is accomplished by using the code RortexUTA and the code Omega-LiutexUTA which are released by Chaoqun Liu at University of Texas at Arlington.
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Project supported by the National Natural Science Foundation of China (Grant No. 51406003).
Biography: Yu-fan Wang (1997-), Male, Master Candidate
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Wang, Yf., Zhang, Wh., Cao, X. et al. The applicability of vortex identification methods for complex vortex structures in axial turbine rotor passages. J Hydrodyn 31, 700–707 (2019). https://doi.org/10.1007/s42241-019-0046-9
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DOI: https://doi.org/10.1007/s42241-019-0046-9