Statistics of Fourier modes in a turbulent flow.
Statistics of Fourier modes in a turbulent flow.
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湍流中傅立叶模态的统计。
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
A. Pumir
中科院分区：
文献类型：
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作者：
C. Brun;A. Pumir
傅里叶级数常用于讨论均匀湍流场的性质。我们调查的湍流速度场和被动标量的傅立叶模式的统计。当系统的尺寸L远大于积分（相关）尺寸l（0）时，已知各个傅立叶模式的统计是高斯的。在20 <或约= R λ <或约= 80的范围内，通过直接数值模拟研究了积分大小为系统大小L约l（0）的情况。在一个给定的Rlambda，我们发现，大的波动的概率变得更大时，波数增加，在定性协议的概念的不稳定性。然而，随着雷诺数的增加，概率密度函数变得更接近高斯，与速度增量的行为形成鲜明对比。我们还表明，在一个简单的级联模型，傅立叶级数分解是不适合捕捉的不稳定性的影响。最后，我们讨论了与我们的结果相关的其他问题。
Fourier series are often used to discuss the properties of a homogeneous turbulent field. We investigate the statistics of Fourier modes of the turbulent velocity field and of a passive scalar. The statistics of individual Fourier modes is known to be Gaussian when the size of the system L is much larger that the integral (correlation) size l(0). The case where the integral size is of the order of the system size L approximately l(0), is studied by direct numerical simulations in the range 20 < or approximately = Rlambda < or approximately = 80. At a given Rlambda, we find that the probabilities of large fluctuations become larger when the wave number increases, in qualitative agreement with the notion of intermittency. As the Reynolds number increases, however, the probability density functions become closer to Gaussian, in sharp contrast with the behavior of velocity increments. We also show that in a simple model of cascade, the Fourier series decomposition is not appropriate to capture intermittency effects. Last, we discuss other issues related to our results.