Abstract
A collimated light beam will be refracted if it propagates through a flow-field with index-of-refraction variations, and its wavefront will be distorted. If we measure the deflection angle of the light beam, the gradient of the wavefront can be obtained using the Malus law, and the wavefront aberration can be computed with a reconstruction algorithm. Two characteristics of background oriented schlieren (BOS) are conducive to wavefront aberration measurement: BOS can be used to measure the deflection angle of a light beam by measuring the displacement field between the reference image and the experiment image. Moreover, in a BOS system of Schlieren mode, only the ray perpendicular to the background image can be captured with a camera. This is helpful to measure wavefront aberrations that occur after a planar wavefront has passed through the flow-field. Based on these characteristics of BOS of Schlieren mode, a new wavefront measurement technique, which is called the BOS-based wavefront technique (BOS-WT), is proposed in this paper. It works by constructing the relationship between the displacement of the background image and the aero-optical wavefront gradient and uses the Southwell wavefront reconstruction algorithm. A BOS-WT system was assembled, and its temporal resolution was found to be 6 ns, and its temporal-correlation resolution reached 0.2 μs. A BOS-WT can measure the time-correlation transient wavefront quantitatively. It is simple and easy to operate. In this paper, we also present a study of the aero-optical performance of supersonic mixing layer based on our BOS-WT transient wavefronts at an interval of 5 μs. The results showed the wavefront was transient and distorted after it had passed through the mixing layer. Through the analysis of the data at the 5 μs interval, the temporal evolution of wavefront can be obtained.
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References
Meier G E A. New optical tools for fluid mechanics. In: Proceedings of the 8th International Symposium on Flow Visualization, Sorrento, Italy, 1998
Sourgen F, Haertig J, George A, et al. Validation of CFD density field in supersonic axisymmetric flow using BOS and differential interferometry. AIAA Paper, 2005, 2005-6036
Sourgen F, Haertig J, Rey C. Comparison between background oriented schlieren measurements (B.O.S.) and numerical simulations. AIAA Paper, 2004, 2004-2602
Elsinga G E, Van Oudheusden B W, Scarano F, et al. Assessment and application of quantitative schlieren methods: Calibrated color schlieren and background oriented schlieren. Exp Fluids, 2004, 36: 309–325
Goldhahn E, Seume J. The background oriented schlieren technique: Sensitivity, accuracy, resolution and application to a three-dimensional density field. Exp Fluids, 2007, 43: 241–249
Venkatakrishnan L, Meier G E A. Density measurements using the background oriented schlieren technique. Exp Fluids, 2004, 37: 237–247
Meier G E A. Computerized background-oriented schlieren. Exp Fluids, 2002, 33: 181–187
Sommersel O K, Bjerketvedt D, Christensen S O, et al. Application of background oriented schlieren for quantitative measurements of shock waves from explosions. Shock Waves, 2008, 18: 291–297
Raffel M, Richard H, Meier G E A. On the applicability of background oriented optical tomography for large scale aerodynamic investigations. Exp Fluids, 2000, 28: 477–481
Hargather M J, Settles G S. Natural-background-oriented schlieren imaging. Exp Fluids, 2010, 48: 59–68
Kindler K, Goldhahn E, Leopold F, et al. Recent developments in background oriented schlieren methods for rotor blade tip vortex measurements. Exp Fluids, 2007, 43: 233–240
Zhao Y X, Yi S H, Tian L F, et al. An experimental study of aero-optical aberration and dithering of supersonic mixing layer via BOS. Sci China: Phys Mech Astron, 2010, 53: 81–94
Southwell W H. Wave-front estimation from wave-front slope measurements. J Opt Soc Am, 1980, 70: 998–1006
Wakamatsu Y, Kanda T, Yatsuyanagi N. Preliminary consideration of hypersonic test vehicle for scramjet engine test. ISTS 2000-g-24, 2000
Chew L. Coherent structures effects on shear layer optics. AIAA Paper, 1990, 90-0185
Yi S H, Hou Z X, Zhao Y X. Supersonic Free-Vortex Aerowindow and Its Optical Quality (in Chinese). Changsha: NUDT Press, 2005
Yi S H, He L, Zhao Y X, et al. A flow control study of a supersonic mixing layer via NPLS. Sci China Ser G: Phys Mech Astron, 2009, 52: 2001–2006
Yi S H, Tian L F, Zhao Y X, et al. Aero-optical aberration measuring method based on NPLS and its application. Chinese Sci Bull, 2010, 55: 3545–3549
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Tian, L., Yi, S., Zhao, Y. et al. Aero-optical wavefront measurement technique based on BOS and its applications. Chin. Sci. Bull. 56, 2320–2326 (2011). https://doi.org/10.1007/s11434-011-4583-z
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DOI: https://doi.org/10.1007/s11434-011-4583-z