Onorato M, Camussi R, Iuso G
Dipartimento di Fisica Generale, Universita di Torino, Via Pietro Giuria 1, 10125 Torino, Italy.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Feb;61(2):1447-54. doi: 10.1103/physreve.61.1447.
The statistical properties of the streamwise velocity fluctuations in a fully developed turbulent channel flow are studied experimentally by means of single hot wire measurements. The intermittency features, studied through the scaling of the moments of the velocity structure function computed using the extended self- similarity and through the probability density function of the wavelet coefficients, are found to be dependent on the distance from the wall. The maximum intermittency effects are observed in the region between the buffer layer and the inner part of the logarithmic region where it is known that the bursting phenomenon, related to coherent structures such as low speed streaks and streamwise vortices, is the dominant dynamical feature. An eduction technique based on wavelet transform for identification of organized motion is developed and used to analyze the turbulent signals. Streamwise velocity conditional averages computed on events educed with the proposed method are reported. Events responsible for intermittency are found to consist of regions of high velocity gradients and are directly correlated with the observed increase of intermittency close to the wall.
通过单根热线测量实验研究了充分发展的湍流槽道流中流向速度脉动的统计特性。通过使用扩展自相似性计算速度结构函数的矩的标度以及小波系数的概率密度函数来研究间歇性特征，发现这些特征取决于离壁面的距离。在缓冲层和对数区域内部之间的区域观察到最大的间歇性效应，已知在该区域中，与诸如低速条纹和流向涡旋等相干结构相关的猝发现象是主要的动力学特征。开发了一种基于小波变换的用于识别有组织运动的提取技术，并用于分析湍流信号。报告了根据所提出的方法提取的事件计算出的流向速度条件平均值。发现导致间歇性的事件由高速梯度区域组成，并且与在靠近壁面处观察到的间歇性增加直接相关。
