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Convective speed of a vortex structure in mixing layer is an important physical quantity for correcting aero-optics caused by the flowfield as a beam passes; however, knowledge about the dynamic characteristics of convective speed of a vortex structure in mixing layer is limited because the convective speed calculated from isentropic model, which is widely used at present, is a constant. Based on the large eddy simulation and ray tracing method, the optical path length (OPL) profile over the mixing layer flowfield as beams pass through the flowfield is calculated and compared with the instantaneous vorticity contours at the same time instant. The analysis of the relationship between the local minimum of OPL in the OPL profile and the position of vortex core shows that the point of the local minimum of OPL just corresponds to the center of the vortex core. Based on this corresponding relation, the position extraction of vortex core, which is a quantitative method of calculating the instantaneous convective speed of a vortex structures in mixing layer, is proposed and validated with the data obtained from direct geometry measurement. Using this quantitative method, the instantaneous convective speeds of vortex structures with different sizes, two vortexes in the process of vortex pairing and merging, and vortex structures in the strongly compressive flowfield are calculated quantitatively and analyzed. Our quantitative results clearly present the characteristics of convective speed of vortex structures in mixing layer as follows. 1) The instantaneous convective velocity of a single vortex structure in the mixing layer flowfield varies with time, that is the fluctuation characteristics, and the fluctuation amplitude also varies with the size of a vortex structure and the compressibility of the flowfield. Specifically, the amplitude is proportional to the size of a vortex and the compressibility of the flowfield. 2) In the process of vortex pairing and merging, the variation ranges of instantaneous convective speeds of the two vortex structures are large. Specifically, the maximum value of instantaneous convective speed is close to the speed of the high-speed layer and the minimum value of instantaneous convective speed is close to the speed of the low-speed layer, and the profile of instantaneous convective speed of each vortex structure in this process approximately shows a shape of sinusoidal curve. 3) The mean value of instantaneous convective speed of a vortex structure in mixing layer is not consistent with the theoretical convective speed of vortex structure, which is calculated from the isentropic model, and the deviation between instantaneous convective speed and theoretical convective speed varies with the size of a vortex structure and the compressibility of the flowfield. In addition, the physical reasons for explaining the characteristics of instantaneous convective speed of the vortex structures in mixing layer are also presented.
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Keywords:
- convective speed /
- mixing layer /
- aero-optics /
- large eddy simulation
[1] Yin X L 2003 Principle of Aero-Optics (Beijing: China Astronautics Press) p2 (in Chinese) [殷兴良 2003 气动光学原理 (北京: 中国宇航出版社) 第2页]
[2] Rogers M M, Moser R D 1992 J. Fluid Mech. 243 183
[3] Mungal M G, Hermanson J C, Dimotakis P E 1985 AIAA J. 23 1418
[4] Monkewitz P A, Huerre P 1982 Phys. Fluids 25 1137
[5] Brown G L, Roshko A 1974 J. Fluid Mech. 64 775
[6] Winant C D, Browand F K 1974 J. Fluid Mech. 63 237
[7] Zhu Y Z, Yi S H, Kong X P, He L 2015 Acta Phys. Sin. 64 064701 (in Chinese) [朱杨柱, 易仕和, 孔小平, 何霖 2015 64 064701]
[8] Gan C J, Li L, Ma H D, Xiong H L 2014 Acta Phys. Sin. 63 054703 (in Chinese) [甘才俊, 李烺, 马汉东, 熊红亮 2014 63 054703]
[9] Gan C J, Li L, Ma H D, Xiong H L 2013 Acta Phys. Sin. 62 184701 (in Chinese) [甘才俊, 李烺, 马汉东, 熊红亮 2013 62 184701]
[10] Dimotaksi P, Catrakis H 2001 J. Fluid Mech. 433 105
[11] Xie W K, Ma H T, Gao Q, Jiang W J 2014 Laser Optoelectron. Prog. 51 090001 (in Chinese) [谢文科, 马浩统, 高穹, 江文杰 2014 激光与光电子学进展 51 090001]
[12] Jumper E J, Ronald J H 1995 AIAA J. 33 2151
[13] Hugo R J, Jumper E J 1997 AIAA J. 35 671
[14] Bogdanoff D W 1983 AIAA J. 21 926
[15] Papamoschou D, Roshko A 1988 J. Fluid Mech. 197 453
[16] Thurow B S, Naibo Jiang, Kim J H, Lempert W, Samimy M 2008 Phys. Fluids 20 066101
[17] Goebel S G, Dutton J C 1991 AIAA J. 29 538
[18] Ren W, Liu H 2012 Proceedings of the 42nd AIAA Fluid Dynamics Conference and Exhibit 2012 New Orleans, USA, June 25, 2012 p1
[19] Wang M Mani A, Gordeyev S 2012 Annu. Rev. Fluid Mech. 44 299
[20] Dimotakis P E, Catrakis H J, Fourgrette D L 2001 J. Fluid Mech. 433 105
[21] Catrakis H J, Aguirre R C, Ruiz-Plancarte J 2002 J. Fluid Mech. 462 245
[22] Aguirre R C, Catrakis H J 2004 AIAA J. 42 1973
[23] Papamoschou D 1991 AIAA J. 29 680
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[1] Yin X L 2003 Principle of Aero-Optics (Beijing: China Astronautics Press) p2 (in Chinese) [殷兴良 2003 气动光学原理 (北京: 中国宇航出版社) 第2页]
[2] Rogers M M, Moser R D 1992 J. Fluid Mech. 243 183
[3] Mungal M G, Hermanson J C, Dimotakis P E 1985 AIAA J. 23 1418
[4] Monkewitz P A, Huerre P 1982 Phys. Fluids 25 1137
[5] Brown G L, Roshko A 1974 J. Fluid Mech. 64 775
[6] Winant C D, Browand F K 1974 J. Fluid Mech. 63 237
[7] Zhu Y Z, Yi S H, Kong X P, He L 2015 Acta Phys. Sin. 64 064701 (in Chinese) [朱杨柱, 易仕和, 孔小平, 何霖 2015 64 064701]
[8] Gan C J, Li L, Ma H D, Xiong H L 2014 Acta Phys. Sin. 63 054703 (in Chinese) [甘才俊, 李烺, 马汉东, 熊红亮 2014 63 054703]
[9] Gan C J, Li L, Ma H D, Xiong H L 2013 Acta Phys. Sin. 62 184701 (in Chinese) [甘才俊, 李烺, 马汉东, 熊红亮 2013 62 184701]
[10] Dimotaksi P, Catrakis H 2001 J. Fluid Mech. 433 105
[11] Xie W K, Ma H T, Gao Q, Jiang W J 2014 Laser Optoelectron. Prog. 51 090001 (in Chinese) [谢文科, 马浩统, 高穹, 江文杰 2014 激光与光电子学进展 51 090001]
[12] Jumper E J, Ronald J H 1995 AIAA J. 33 2151
[13] Hugo R J, Jumper E J 1997 AIAA J. 35 671
[14] Bogdanoff D W 1983 AIAA J. 21 926
[15] Papamoschou D, Roshko A 1988 J. Fluid Mech. 197 453
[16] Thurow B S, Naibo Jiang, Kim J H, Lempert W, Samimy M 2008 Phys. Fluids 20 066101
[17] Goebel S G, Dutton J C 1991 AIAA J. 29 538
[18] Ren W, Liu H 2012 Proceedings of the 42nd AIAA Fluid Dynamics Conference and Exhibit 2012 New Orleans, USA, June 25, 2012 p1
[19] Wang M Mani A, Gordeyev S 2012 Annu. Rev. Fluid Mech. 44 299
[20] Dimotakis P E, Catrakis H J, Fourgrette D L 2001 J. Fluid Mech. 433 105
[21] Catrakis H J, Aguirre R C, Ruiz-Plancarte J 2002 J. Fluid Mech. 462 245
[22] Aguirre R C, Catrakis H J 2004 AIAA J. 42 1973
[23] Papamoschou D 1991 AIAA J. 29 680
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