Effects of multiscale geometry on the large-scale coherent structures of an axisymmetric turbulent jet
Effects of multiscale geometry on the large-scale coherent structures of an axisymmetric turbulent jet
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多尺度几何对轴对称湍流射流大尺度相干结构的影响
DOI：
10.1007/s12650-018-0479-1
复制
发表时间：
2018
影响因子：
1.7
通讯作者：
Breda M
中科院分区：
文献类型：
--
作者：
Breda M
摘要本文研究了多尺度几何结构对轴对称湍流射流近场结构的影响。借助于层析粒子图像测速技术，分析了由于这种分形几何结构的相干结构的抑制，并评估了近场涡量的变化。这种特殊的几何形状导致圆射流的方位角涡环破裂，并形成径向和流向相反符号的涡量斑块。后者被认为是负责轴切换的射流，观察到的一些非圆形射流的长轴收缩和短轴扩大在近场的现象，有效地切换两个轴的射流。据作者所知，这是第一次在相干结构被抑制的射流中观察到轴切换。在近场发现显著差异之后，检查远场。在那里，发现大尺度漩涡的积分长度尺度和根据喷流半宽评估的喷流尺寸以类似的方式演变，而分形喷流的比例高于圆形喷流，其中近场结构尚未被抑制。图形摘要
AbstractIn this study, the effect of multiscale geometry on the near-field structure of an axisymmetric turbulent jet is examined at a global Reynolds number of. With the aid of tomographic particle image velocimetry, the suppression of the coherent structures due to this fractal geometry is analysed and the changes to the near-field vorticity are evaluated. This particular geometry leads to the breakup of the azimuthal vortex rings present for round jets and to the formation of radial and streamwise opposite-signed patches of vorticity. The latter are found to be responsible for the axis switching of the jet, a phenomenon observed for some noncircular jets where the major axis shrinks and the minor one expands in the near field, effectively switching the two axes of the jet. This was the first time, to the knowledge of the authors, that axis switching has been observed for a jet where the coherent structures have been suppressed. Following the significant differences found in the near field, the far field is examined. There, the integral lengthscale of the large scale eddiesand the size of the jet evaluated in terms of the jet half-widthare found to evolve in a similar fashion, whilst the ratiois found to be higher for the fractal jet than for the round jet, for which the near-field structures have not been suppressed.Graphical abstract
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轴对称分形强制湍流射流的近场和远场分析
DOI：
--
发表时间：
2017
期刊：
影响因子：
--
作者：
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通讯作者：
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DOI：
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发表时间：
2014
期刊：
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影响因子：
4.6
作者：
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DOI：
--
发表时间：
2012
期刊：
影响因子：
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