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通过使用一排16根冷线探头排在多个空间点同时测量微加热圆柱的尾流温度场, 用小波分析技术对瞬时温度场的时间序列信号进行多尺度分析, 目的是研究不同尺度脉动温度对总体温度场的贡献.直径为d = 12.7 mm 的圆柱产生了被测的尾流, 对应的雷诺数为5500, 测量区域位于下游距离为2d 和 20d 之间. 基于小波多尺度分辨技术, 尾流温度场被分解为不同温度脉动特征尺度的小波分量. 通过分析这些小波分量的瞬时温度等值线图, 能够直接观测到不同特征尺度的涡结构运动特征和湍流间歇过程. 特别地, 我们在近场区从原始信号分解获得的高频区域中发现了K-H涡的存在. 不同尺度的温度方差沿流向的变化表明, 在下游距离为x=3d和 20d之间, 中等尺度的结构比大尺度和小尺度结构对总的温度均方根的贡献更大. 不同尺度的自相关函数表明, 大尺度和中等尺度的结构显示出较大的相关性, 而高频的小波分量则更快地失去了原有的拟序性.A wavelet multi-resolution technique is applied to analysing the temperature field simultaneously obtained by a rake of 16 cold-wires in the turbulent near-wake of a slightly heated circular cylinder with a diameter of d = 12.7 mm in a range of x/d from 3 to 20, where x is the downstream distance from the cylinder axis. This technique enables us to decompose the fluctuating temperature field into a number of wavelet components based on different characteristic frequency bandwidths or scales, which are representative of the temperature fields of different scales. The turbulent mixing characteristics of various fluctuating scales are examined in terms of instantaneous temperature contours of each wavelet component. The flow structures and intermittent processing of various scales are visualized. The streamwise evolutions of temperature variance of various scales suggest that the intermediate-scale structures make larger contribution to the total temperature than the large- and small-scale structures. The wavelet auto-correlation function indicates that the large- and intermediate-scale structures display larger correlation and the wavelet component of higher frequency loses coherence quickly.
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Keywords:
- turbulent wake /
- passive scalar /
- wavelets
[1] Lepore J, Mydlarski L 2009 Phys. Rev. Lett. 103 034501
[2] Fernando L P, Hassan A 2004 Phys. Rev. Lett. 93 084501
[3] Rinoshika A, Zhou Y 2005 J. Fluid Mech. 524 229
[4] Rinoshika A, Zhou Y 2005 Phys. Rev. E 71-4 057504
[5] Rinoshika A, Zhou Y 2007 Int. Heat and Fluid Flow 28 948
[6] Freymuth P, Uberoi M 1971 Phys. Fluids 14 2574
[7] LaRue J C, Libby P A 1974 Phys. Fluids 17 873
[8] Sreenivasan K R 1981 Phys. Fluids 24 1232
[9] Antonia R A, Browne L W B 1986 J. Fluid Mech. 163 393
[10] Mi J, Antonia R A 1999 Int. Community Heat Mass Transfer 26 45
[11] Mi J, Xu M, Antonia R A, Wang J J 2011 Experiments in Fluids 50 429
[12] Daubechies I 1992 No 61 Society for Industrial and Applied Mathematics Philadelphia, 1992 p357
[13] Li H 1998 J. Fluids Engineering 120 778
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[1] Lepore J, Mydlarski L 2009 Phys. Rev. Lett. 103 034501
[2] Fernando L P, Hassan A 2004 Phys. Rev. Lett. 93 084501
[3] Rinoshika A, Zhou Y 2005 J. Fluid Mech. 524 229
[4] Rinoshika A, Zhou Y 2005 Phys. Rev. E 71-4 057504
[5] Rinoshika A, Zhou Y 2007 Int. Heat and Fluid Flow 28 948
[6] Freymuth P, Uberoi M 1971 Phys. Fluids 14 2574
[7] LaRue J C, Libby P A 1974 Phys. Fluids 17 873
[8] Sreenivasan K R 1981 Phys. Fluids 24 1232
[9] Antonia R A, Browne L W B 1986 J. Fluid Mech. 163 393
[10] Mi J, Antonia R A 1999 Int. Community Heat Mass Transfer 26 45
[11] Mi J, Xu M, Antonia R A, Wang J J 2011 Experiments in Fluids 50 429
[12] Daubechies I 1992 No 61 Society for Industrial and Applied Mathematics Philadelphia, 1992 p357
[13] Li H 1998 J. Fluids Engineering 120 778
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