The growth of large scales at defect sites in the plane mixing layer
The growth of large scales at defect sites in the plane mixing layer
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平面混合层缺陷处大尺度的生长
DOI：
10.1017/s0022112093000497
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发表时间：
1993
影响因子：
3.7
通讯作者：
F. Browand
中科院分区：
文献类型：
--
作者：
T. Dallard;F. Browand
涡结构的演变在附近的图案缺陷或位错，实验产生的强制高雷诺数混合层，研究使用一个新的二维小波变换称为弧。这种变换将光谱信息定位在物理空间中-就像所有小波一样-但在波数空间中不是方向特定的。各种类型的强迫，包括强迫在基波和次谐波波数，产生一系列的混合层的反应。最重要的发现是，一个位错网站作为一个核心，并启动了快速，局部的演变，以更大的规模。局部“斑块”的面积大约随着下游距离的平方而增长。缺陷引起的斑片与圆柱尾流中的扰动区具有一般的相似性--最近许多研究者对此进行了评论--特别是与威廉姆森（1992）描述的Λ结构。
The evolution of vortex structure in the vicinity of a pattern defect or dislocation, generated experimentally by forcing a high Reynolds number mixing layer, is studied using a new two-dimensional wavelet transform called Arc. This transform localizes spectral information in physical space – as all wavelets do – but is not direction-specific in wavenumber space. Various types of forcing, including forcing at the fundamental and subharmonic wavenumbers, produce a range of mixing-layer responses. The most significant finding is that a dislocation site acts as a nucleus and initiates a rapid, localized evolution to larger scales. The area of the localized ‘patch’ grows approximately as the square of downstream distance. Defect-initiated patches bear generic similarities to the disturbed regions in cylinder wakes – commented upon recently by many researchers – and in particular to the Λ-structures described by Williamson (1992).