热混合层中温度脉动的多重分形特性

Multifractal Properties of Fluctuating Temperatures in Thermal Mixing Layers

运用广义计盒维数方法，对测量热混合层所得到的温度脉动时间序列信号进行了详细研究，发现等温截面的时间点集在一定尺度范围内表现出多重分形几何特性，并计算了截面阀值的绝对值范围为０～１．５ 时的等温截面的多重分形的广义计盒维数Ｄｑ，当ｑ ３，Ｄｑ 随截面阀值Ｈ以及测量点位置Ｙ的变化不大，热混合层温度脉动时间序列具有统一的多重分形维数；但当ｑ ＞ ３，Ｄｑ 受湍流流场本身的影响很大．

The geometrical properties of isotherm surface in thermal mixing layer are studied using a generalized box counting method applied to the temperature time series data measured by a cold wire probe. The generalized dimensions D q are calculated with the range of absolute value of interface threshold H varying from 0 to 1.5. It is found that when q3, the D q with varies little interface threshold H and probe location Y and the same multifractal dimension of fluctuating temperature time series data in thermal mixing layers can be obtained. However, when q>3 the influence of H and Y on D q can not be ignored.