Drag reduction in turbulent channel flow by phase randomization
Drag reduction in turbulent channel flow by phase randomization
复制标题
通过相位随机化减少湍流通道流的阻力
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
L. Sirovich
中科院分区：
文献类型：
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作者：
R. Handler;E. Levich;L. Sirovich
本文给出了平面槽道湍流的数值模拟结果，其中引入了一种强迫，这种强迫来自于所选傅立叶模的随机化。在所有情况下，随机化在整个信道中均匀地引入。由此产生的湍流的性质强烈依赖于波数，其相位是随机的和强迫频率。选择了两个主要波数带。第一个包括湍流的最大长度尺度的选定子集。在这个带中的强迫导致完全持续的最大质量通量增加，高于正常湍流的30%，这转化为58%的阻力减小。以这种方式产生的模拟减阻湍流的许多统计特性与实验中观察到的湍流统计特性定性一致，在实验中，通过将低浓度的长链聚合物引入流中来实现减阻。在第二组模拟中，中间波长和最小波长的相位被随机化。在这些运动尺度上的强迫导致阻力增加。对相随机化减阻的机理进行了推测。
Results of numerical simulations of plane turbulent channel flow are presented in which a forcing is introduced which derives from the randomization of selected Fourier modes. In all cases, the randomization is introduced uniformly throughout the channel. The properties of the resulting turbulence are strongly dependent on both the wave numbers whose phases are randomized and the forcing frequency. Two principal wave‐number bands have been selected. The first includes a selected subset of the largest length scales of the turbulence. Forcing in this band results in a fully sustained maximum mass flux increase above that of normal turbulence of 30%, which translates into a drag reduction of 58%. Many of the statistical properties of the simulated drag‐reduced turbulence generated in this manner are in good qualitative agreement with the statistical properties of turbulence observed in experiments in which drag reduction is achieved through the introduction of small concentrations of long‐chained polymers into the flow. In a second set of simulations, the phases of the intermediate and smallest wavelengths were randomized. Forcing at these scales of motion results in a drag increase. Speculations on the mechanism of the drag reduction by phase randomization are offered.