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The fine flow structure over backward facing step with supersonic injection at the free-stream Mach number of 3.4 is investigated via nano-tracer planar laser scattering (NPLS). The Mach number of injection is measured to be 2.45 actually, even though designed to be 2.5 nominally. The shock wave, shear layer, mixing layer, Kelvin-Helmholtz vortex, horn-like vortex, coherent structures, etc, are clearly revealed. Flow images with the high spatiotemporal resolution are captured involving the streamwise and spanwise flow field in planes at different heights. Based on a large number of fine images, the spatial correlation analysis is conducted to reveal the structure scale and incline angle. The results indicate that with the flow developing, the structure angle tends to be larger and the structure scale becomes smaller. While the injection is working, the downstream surface of step will be covered by a thin film layer. In addition, the schlieren technique is used to compare with NPLS results, and the surface pressure coefficients are measured. In the downstream of injection, the coefficient is 0.0146. The fractal dimensions of different zones in NPLS image are calculated, showing that in the initial stage of flow the fractional dimension is approximate to 1 and the closer to downstream, the higher the dimension is.
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Keywords:
- supersonic /
- backward facing step /
- injection /
- flow structures
[1] Li G C 2006 Aero-Optics (Beijing: National Defense Industry Press) (in Chinese) [李桂春2006气动光学(北京: 国防工业出版社)]
[2] Eckert E R G 1953 Heat-Transfer Symposium University of Michigan USA 195
[3] Philippe R 2007 AIAA paper 2007-5747
[4] Seban R A, Back L H 1962 J. Heat Trans. 84 45
[5] Hargather M J, Settles G S 2010 AIAA Paper 2010-4206
[6] Meyer T R 2002 Exp. Fluids 32 603
[7] Elliott G S, Glumac N, Carter C D 1999 AIAA Paper 1999 0643
[8] Zhu Y Z, Yi S H, He L, Tian L F, Zhou Y W 2013 Chin. Phys. B 22 014702
[9] Zhu Y Z, Yi S H, Kong X P, Quan P C, Chen Z, Tian L F 2014 Acta Phys. Sin. 63 134701 (in Chinese) [朱杨柱, 易仕和, 孔小平, 全鹏程, 陈植, 田立丰 2014 物理学报 63 134701]
[10] Zhao Y X, Yi S H, Tian L F, Cheng Z Y 2009 Sci. China E 52 3640
[11] Zhao Y X, Yi S H, He L, Tian L F, Cheng Z Y 2007 Chin. Sci. Bull. 52 1297
[12] Zhao Y X, Yi S H, Tian L F, He L, Cheng Z Y 2008 Sci. China G 51 1134
[13] Yi S H, He L, Zhao Y X, Tian L F, Cheng Z Y 2009 Sci. China G 52 2001
[14] Sreenivasan K R, Meneveau C 1986 J. Fluid Mech. 173 357
[15] Zhao Y X, Yi S H, Tian L F, He L, Cheng Z Y 2009 Sci. China G 51 1134
[16] Bourdon C J, Dutton J C 1999 Phys. Fluids 11 201
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[1] Li G C 2006 Aero-Optics (Beijing: National Defense Industry Press) (in Chinese) [李桂春2006气动光学(北京: 国防工业出版社)]
[2] Eckert E R G 1953 Heat-Transfer Symposium University of Michigan USA 195
[3] Philippe R 2007 AIAA paper 2007-5747
[4] Seban R A, Back L H 1962 J. Heat Trans. 84 45
[5] Hargather M J, Settles G S 2010 AIAA Paper 2010-4206
[6] Meyer T R 2002 Exp. Fluids 32 603
[7] Elliott G S, Glumac N, Carter C D 1999 AIAA Paper 1999 0643
[8] Zhu Y Z, Yi S H, He L, Tian L F, Zhou Y W 2013 Chin. Phys. B 22 014702
[9] Zhu Y Z, Yi S H, Kong X P, Quan P C, Chen Z, Tian L F 2014 Acta Phys. Sin. 63 134701 (in Chinese) [朱杨柱, 易仕和, 孔小平, 全鹏程, 陈植, 田立丰 2014 物理学报 63 134701]
[10] Zhao Y X, Yi S H, Tian L F, Cheng Z Y 2009 Sci. China E 52 3640
[11] Zhao Y X, Yi S H, He L, Tian L F, Cheng Z Y 2007 Chin. Sci. Bull. 52 1297
[12] Zhao Y X, Yi S H, Tian L F, He L, Cheng Z Y 2008 Sci. China G 51 1134
[13] Yi S H, He L, Zhao Y X, Tian L F, Cheng Z Y 2009 Sci. China G 52 2001
[14] Sreenivasan K R, Meneveau C 1986 J. Fluid Mech. 173 357
[15] Zhao Y X, Yi S H, Tian L F, He L, Cheng Z Y 2009 Sci. China G 51 1134
[16] Bourdon C J, Dutton J C 1999 Phys. Fluids 11 201
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