论文标题
基于小波的检测器功能，用于表征间歇性速度信号
A wavelet-based detector function for characterizing intermittent velocity signals
论文作者
论文摘要
在这项工作中，我们提出了一个基于小波变换的新检测功能，以区分间歇性速度信号中的湍流和非扰动区域。基于导数的检测器函数通常用于间歇性计算方案，显示了信号的湍流部分内的大波动，并且需要在某个``平滑周期''上平均以消除假掉落，从而在计算间歇性中引入了主观性。通过在整个频率范围内平均````pre-Multipled小波'''''获得``此处提出的新检测器函数''，从而导致一个比基于衍生的检测器更光滑的函数，同时具有良好的歧视性属性。这使得平滑时期的选择不必要，并消除了与之相关的主观性。我们证明了Hedley and Keffer（1974，J。Fluid Mech。，V64，pp625）在广泛使用方法的框架内的小波探测器的有效性，用于代表不同阶段的速度信号，这些速度信号代表了粗糙度诱导的过渡的不同阶段。小波探测器函数在检测规范湍流边界层的边缘间歇性方面非常有效，从而突出了其通用性。原则上，我们的检测器可以与任何指定阈值获取指标函数的方法一起使用。
In this work, we propose a new detector function based on wavelet transform to discriminate between turbulent and non-turbulent regions in an intermittent velocity signal. The derivative-based detector function, which is commonly used in intermittency calculation schemes, shows large fluctuations within turbulent parts of the signal and requires averaging over a certain ``smoothing period'' to remove the fake drop-outs, introducing subjectivity in calculating intermittency. The new detector function proposed here is obtained by averaging the ``pre-multiplied wavelet energy'' over the entire frequency range, resulting in a function that is much smoother than the derivative-based detector and at the same time has a good discriminatory property. This makes the choice of the smoothing period unnecessary and removes the subjectivity associated with it. We demonstrate the effectiveness of the wavelet detector within the framework of the widely-used method by Hedley and Keffer (1974, J. Fluid Mech., V64, pp625), for a range of velocity signals representing the different stages of roughness-induced transition. The wavelet detector function works well in detecting the edge intermittency of a canonical turbulent boundary layer as well, thereby highlighting its generality. Our detector can, in principle, be used with any method of specifying threshold for obtaining an indicator function.
