Velocity and Temperature Dissimilarity in the Surface Layer Uncovered by the Telegraph Approximation
Velocity and Temperature Dissimilarity in the Surface Layer Uncovered by the Telegraph Approximation
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DOI：
10.1007/s10546-021-00632-2
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发表时间：
2021-06
影响因子：
4.3
通讯作者：
Kelly Y. Huang;G. Katul;M. Hultmark
中科院分区：
文献类型：
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作者：
Kelly Y. Huang;G. Katul;M. Hultmark
物理学家、数学家马尚昆曾经说过：“最简单的变量就是一个可以有两个值的变量。如果只有一个值，则不可能发生变化。在此基础上，将电报近似(TA)应用于美国犹他州盐滩上空一米处的流向速度分量和气温时间序列。TA技术消除了幅度变化，只保留了湍流序列中的过零行为，从而允许单独检查集群在间歇性中的作用。通过应用TA技术，分析了不稳定、近中性和稳定大气层结中温度和速度的不同群聚特性。考察了原始和TA序列的谱指数，惯性-子程行为符合先前的经验关系，而含能范围则表现出偏差。在TA系列运行密度波动的标准差中观察到了这两个不同的标度区域，描绘了细尺度和大尺度之间的标度行为。在细尺度上，集群不受稳定机制的显著影响，并且比大尺度上要高。在大尺度上，温度序列表现出较强的聚集性且稳定性增强，在稳定条件下与流向速度分量序列相比具有更高的聚集性。在小的速度范围内，振幅的变化可以减轻间歇性，但在温度的间歇性中，幅度的变化只起到很小的作用。最后，探讨了脉间周期概率分布，并讨论了作为TA湍流模型的自组织临界性的意义。
The physicist and mathematician Shang-Keng Ma once commented that “the simplest possible variable is one that can have two values. If there is only one value, no variation is possible." Guided by this dictum, the telegraphic approximation (TA) is applied to the streamwise velocity component and air temperature time series acquired in the first metre above the salt flats of Utah, USA. The TA technique removes amplitude variations and retains only zero-crossing behaviour in a turbulent series, thereby allowing for an isolated examination of the role of clustering in intermittency. By applying the TA technique, clustering properties are analyzed to uncover dissimilarity in temperature and velocity across unstable, near-neutral, and stable atmospheric stratification. The spectral exponents of the original and of the TA series are examined, with the inertial-subrange behaviour conforming to prior empirical relations and the energy-containing range exhibiting deviations. These two distinct scale regimes are observed in the standard deviations of the running density fluctuations of the TA series, delineating scaling behaviour between fine and large scales. In the fine scales, clustering is not appreciably affected by the stability regime and is higher than in the large scales. In the large scales, the temperature series exhibits stronger clustering with increasing stability, and higher clustering compared with the streamwise velocity component series under stable conditions. Amplitude variations are shown to mitigate intermittency in the small scales of velocity, but play only a minor role in intermittency for temperature. Last, the inter-pulse period probability distributions are explored and implications to self-organized criticality as models for TA turbulence are discussed.