解耦湍流中间歇性流动结构对反常标度和多重分形性的贡献
Disentangling intermittent flow structure contributions to anomalous scaling and multifractality in turbulence
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中文总结 AI 辅助
本研究通过阈值化涡量并反演毕奥-萨伐尔定律的滤波方法，解耦了湍流中间歇性流动结构对反常标度和多重分形性的贡献，揭示了其对相关物理量的选择性影响。
中文摘要 AI 辅助
湍流的间歇性表现为强涡旋和耗散的尖锐峰值，它导致柯尔莫哥洛夫简单自相似理论失效，引发反常标度、多重分形性等现象，至今仍无法用完整的理论描述。间歇性流动结构如何影响这些不同的测量结果目前尚不明确。通过一种简单的滤波程序——阈值化涡量并反演毕奥-萨伐尔定律以生成滤波后的速度场，我们证明可以解耦间歇性流动结构的影响。当滤除速度场中极端涡量的贡献时，能谱标度保持不变，瓶颈效应被展平，结构函数标度趋近于柯尔莫哥洛夫值。该方法对横向指数的处理更迅速，揭示了强旋流区域的选择性重要性。类似地，随着间歇性被滤除，多重分形性的程度降低，粗糙度奇异指数的范围缩小。剩余场意外地表现出更强的多重分形性，但其结构开始脱离潜在的湍流骨架。我们量化了其对涡旋拉伸和应变自放大的影响。本研究表明，毕奥-萨伐尔方法可选择性地去除湍流及其标度中的间歇性效应。
英文摘要
Intermittency in turbulence manifests as intense vortices and sharp peaks of dissipation. Causing the breakdown of Kolmogorov's simple self-similar theory, it leads to anomalous scaling, multifractality and so far remains beyond the scope of a complete theoretical description. How intermittent flow structures influence these different measurements is not known quantitatively. With a simple filtering procedure-thresholding vorticity and inverting the Biot-Savart law to generate filtered velocity fields-we show the effects of intermittent flow structures can be disentangled. As extreme vorticity contributions to the velocity field are filtered out, the energy spectrum scaling persists, while the bottleneck is flattened, and structure function scalings tend towards their Kolmogorov values. The approach is more rapid for transverse exponents, revealing the selective importance of intensely swirling flow regions. Similarly, the extent of multifractality reduces as intermittency is filtered, shrinking the range of roughness singularity exponents. The residual fields are curiously more multifractal, but their structure begins to break away from an underlying turbulence skeleton. The effects on vortex stretching and strain self-amplification are quantified. Our work shows that a Biot-Savart approach can selectively remove the effects of intermittency from turbulence, and hence from its scalings.
