子波方法提取Rayleigh-Bnard对流温度信号的相干结构

Extracting Coherent Structure from Temperature Data in Rayleigh-Bénard Convection by Wavelet Transformation

采用子波分析方法 ,对 Rayleigh- Bénard对流中温度脉动信号进行了分析 ,根据子波系数方差取极大值的判别准则 ,确定出了对应于温度信号相干结构的尺度或频率 ,然后采用给出的确定尺度下的连续子波反变换公式 ,不需要加入任何门限 ,提出了温度信号相干结构所对应的波形。为证明该方法的有效性 ,还对一个给定的“余弦相干信号 +随机噪声信号”,进行了提取余弦相干信号的数值实验 ,结果表明 ,该方法能够较准确地提取出代表相干结构的余弦信号。

In this paper,wavelet transformation is used to analysis the temperature signals in Rayleigh-Bénard convection.By means of the criterion,i.e.the variance of coefficient of wavelet transformation reaches maximum at a given scale,the corresponding scale or frequency of coherent structure can been obtained automatically.Based on a new reconstruction (or inverse) formula at this scale,the coherent structure can be extracted successfully and no threshold is added.In order to prove the validity of this method,one numerical test,to extract coherent structure from a known signal which is composed of 'cosine+noise'signal,has been accomplished.The results show that the coherent structure involving the signals can be well extracted by using this method.