Measurements of Wavenumber-Celerity Spectrum in Plane and Axisymmetric Jets
Measurements of Wavenumber-Celerity Spectrum in Plane and Axisymmetric Jets
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DOI：
10.2514/3.7747
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发表时间：
1981
期刊：
影响因子：
2.5
通讯作者：
A. Hussain;A. R. Clark
中科院分区：
文献类型：
--
作者：
A. Hussain;A. R. Clark
本文用数字化热线数据计算了平面和轴对称自由空气射流近场和远场的波数-对流速度谱W（k，U）。该谱是时空关联R（S，T）的双傅立叶变换，是在3.18 × 140厘米平面喷流和2.54厘米轴对称喷流中得到的。对于两种射流，出口平均速度Ue为30 m/s。参考（上游）探针对于近场数据位于x/d= 8处，对于远场数据位于x/d=30处，d表示出口直径或狭缝宽度。光谱表明，射流的特点是充满活力的大尺度结构，不仅在近场（略下游的潜在核心），但也在自我保护的区域。最大能量涡的流向长度尺度与射流宽度成比例增加。这些涡的流向长度尺度在圆形射流中约为局部射流宽度的3倍，在平面射流中约为局部射流宽度的3.5倍。在平面射流中，两个区域之间的主导涡的对流速度U从约0.5U e减小到约0.5U e;在轴对称射流中，两个区域之间的主导涡的对流速度U从约0.73U e减小到约0.25f/L。随着涡流尺寸的增加，对流速度U的分散随着W（k，U）逐渐向高于当地时间平均速度U的值倾斜而增加。
The wavenumber-convection velocity spectra W(k, U) in the near and far fields of plane and axisymmetric free air jets have been computed from digitized hot-wire data. This spectrum, which is the double Fouriertransformation of the space-time correlation R(S,T) was obtained in a 3.18 X140 cm plane jet and in a 2.54-cmdiam axisymmetric jet. For both jets the exit mean velocity Ue was 30 m/s. The reference (upstream) probe was located at x/d= 8 for the near-field data and at x/d=30 for the far-field data, d denoting the exit diameter or slit width. The spectra indicate that the jets are characterized by energetic large-scale structures not only in the near field (slightly downstream of the potential core) but also in the self-preserving region. The stream wise length scale of the most energetic eddies increases in proportion with that of the jet width. The stream wise length scale of these eddies is about 3 times the local jet width in the circular jet and 3.5 times the local jet width in the plane jet. The convection velocity U of the dominant eddies decreases from about O.SUe to Q.5Ue between the two regions in the plane jet and from about 0.73Ue to 0.25 f/^ between the two regions in the axisymmetric jet. With increasing eddy sizes, the dispersion in the convection velocity U increases as W(k,U) becomes progressively skewed towards (/values higher than the local time mean velocity U.