用能量最大准则确定VITA法的平均周期

引入了子波变换的方法来确定检测壁湍流猝发事件的VITA法的短时间平均周期T。为了确定VITA法的短时间平均周期T，用子波变换对热膜测速仪测量得到的湍流边界层近壁区域的流向脉动速度的时间序列进行了分解，分解在时域和频域同时进行，根据每一个尺度的子波系数的模的平方在时域的积分得到壁湍流每一个尺度的脉动动能随尺度的分布，用能量最大准则确定与壁湍流猝发事件的时间尺度对应的能量最大的尺度，该尺度也就是VITA法的短时间平均周期T。

DETERMINATION OF THE SHORT TIME AVERAGE INTERVAL IN VITA METHOD BY MAXIMUM ENERGY CRITERION

Wavelet transform is introduced to determine the short timeaverage interval T of VITA incorporating burst event detection in wallturbulence. To determine the short time average interval T of VITA,Wavelet transform is performed to unfold the longitudinal fluctuatingvelocity time series measured in the near wall region of a turbulentboundary layer using hot-film anemometer. This unfolding is carried out both in timespace and in scale space simultaneously. The splitting of kinetic of thelongitudinal fluctuating velocity time series among different scales isobtained by integrating the square of wavelet coefficient modulus intemporal space. The time scale that corresponds to burst events and sois nothing but the short time average interval T of VITA is ascertained by maximumcriterion of the kinetic energy evolution across scales.