Downstream evolution of the most energetic modes in a turbulent axisymmetric jet at high Reynolds number. Part 2. The far-field region
Downstream evolution of the most energetic modes in a turbulent axisymmetric jet at high Reynolds number. Part 2. The far-field region
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高雷诺数湍流轴对称射流中最具能量模式的下游演化。
DOI：
10.1017/s0022112004000175
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发表时间：
2004
影响因子：
3.7
通讯作者：
W. George
中科院分区：
文献类型：
--
作者：
Stephan Gamard;D. Jung;W. George
采用正交分解（POD）方法对湍流轴对称射流的两点速度分量在时间和方位方向上的重傅里叶变换进行了研究，研究了湍流轴对称射流远场高能特征的演化。使用两种不同的实验技术，139个长热线阵列和15个热线铰接式阵列，在射流出口雷诺数从40000到84700的下游15到69直径处进行测量。发现远喷流的POD特征谱比单点统计量更早地遵循平衡相似标度。第一个POD特征谱占解析的流向能量的50%以上，有三个主要峰：近零频率下方位角模2处的主峰，恒定局域Strouhal数$f \delta_{1/2}/U_c$处的主峰，以及近零频率下方位角模0处的小峰。特征谱与下游位置无关，但与本文第1部分中早在$x/D\,{=}\,6$时得到的特征谱相似。所有特征谱在频率上的积分在方位角模式-2处达到峰值。
The evolution of the most energetic features in the far-field region of a turbulent axisymmetric jet are investigated by applying the proper orthogonal decomposition (POD) to the double Fourier transform in time and azimuthal direction of the two-point velocity correlations of the streamwise velocity component. Measurements were obtained from 15 to 69 diameters downstream at jet exit Reynolds numbers ranging from 40 000 to 84 700 using two different experimental techniques, an array of 139 long hot wires and an articulated array of 15 hot wires. The POD eigenspectra for the far jet were found to follow equilibrium similarity scaling sooner than the single-point statistics. The first POD eigenspectrum accounts for more than 50% of the resolved streamwise energy, and has three major peaks: a dominant one at azimuthal mode-2 for near-zero frequency, another at mode-1 at a constant local Strouhal number, $f \delta_{1/2}/U_c$, and a third smaller one for azimuthal mode-0 at near-zero frequency. The eigenspectra were independent of downstream position, but similar to those obtained as early as $x/D\,{=}\,6$ in Part 1 of this paper. All the eigenspectra integrated over frequency peaked at azimuthal mode-2.