潜艇模型尾流场脉动速度及压力的子波自相关分析

Wavelet analysis on the auto-correlation of the wall pressure fluctuating and velocity in the wake of submarine model

采用热线风速仪和压力传感器同时测量潜艇尾流边界层的脉动压力和脉动速度信号,运用连续子波变换的自相关和互相关分析,研究边界层相干结构的变化规律。结果显示,相干结构在时空中呈多尺度分布,在对数区主要集中在大尺度,在缓冲区扩散到小尺度。在大尺度向小尺度的过渡过程中,相关性下降很快,小尺度涡相关性更弱。广泛存在的相关性很弱的小尺度涡成为数量巨大、含能很少的背景湍流。子波变换的自相关分析可以定性,也可以定量显示涡的时空特性,是研究湍流多尺度相干结构的有效方法。

The velocity and wall pressure time sequence in the tail boundary layer of submarine were measured with pressure transducer and the Hot Wire/Film Anemometer.Continuous wavelet auto-correlation was adopted to analyze the coherent structures of turbulent boundary layer.The result shows that coherent structures in space-time domain are of multiple scales.Besides, in the logarithmic layer coherent structures focus on large scales while in the buffer layer they extend to small ones.During the large scales extend to small scales, the correlation drops off rapidly. Many small scales vortices with feeble correlation and little energy from turbulent background.The wavelet auto-correlation analysis can be used to determine the characters of coherent structures in space-time domain in trems of quantity and quality, which is proved to be effictive for multi-scale coherent turbulent structure study.