Regeneration of turbulent fluctuations in low-Froude-number flow over a sphere at a Reynolds number of 3700
Regeneration of turbulent fluctuations in low-Froude-number flow over a sphere at a Reynolds number of 3700
复制标题
雷诺数为 3700 的球体上低弗劳德数流的湍流波动的再生
DOI：
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发表时间：
2016
影响因子：
3.7
通讯作者：
E. Balaras
中科院分区：
文献类型：
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作者：
Anikesh Pal;S. Sarkar;A. Posa;E. Balaras
直接数值模拟（DNS）进行研究的行为，通过一个球体在政权的高分层（低弗劳德数$Fr$）。与先前的结果在较低的雷诺数，这表明单调抑制湍流的分层流过去的一个球体，它被发现，低于临界$Fr$，增加分层诱导非定常涡运动和湍流波动在近尾流。通过计算能量谱、湍流能量方程、能量在水平和垂直分量中的分配以及浮力雷诺数，对近尾流进行量化。这些诊断表明，浮力的稳定作用将球体上的流动改变为球体周围的流动。流动的这种质的变化导致在水平面内的非定常旋涡脱落的新状态和导致湍流再生的增强的水平剪切。
Direct numerical simulations (DNS) are performed to study the behaviour of flow past a sphere in the regime of high stratification (low Froude number $Fr$ ). In contrast to previous results at lower Reynolds numbers, which suggest monotone suppression of turbulence with increasing stratification in flow past a sphere, it is found that, below a critical $Fr$ , increasing the stratification induces unsteady vortical motion and turbulent fluctuations in the near wake. The near wake is quantified by computing the energy spectra, the turbulence energy equation, the partition of energy into horizontal and vertical components, and the buoyancy Reynolds number. These diagnostics show that the stabilizing effect of buoyancy changes flow over the sphere to flow around the sphere. This qualitative change in the flow leads to a new regime of unsteady vortex shedding in the horizontal planes and intensified horizontal shear which result in turbulence regeneration.