喷雾射流中粒度、时间和速度信号的双重自仿射性

DYADIC SELF-AFFINITY OF DIAMETER,TRANSMIT TIME AND VELOCITY SIGNALS OF DROPLETS IN AIR BLAST SPRAY

采用双模颗粒动态分析仪 (DualPDA)同时测定了气流式喷嘴雾化过程中液滴在不同空间位置的三维速度向量、粒度和滞留时间等物理量 ,研究了液滴速度分量、粒度分布及滞留时间的时间序列 ,通过域重新标度分析法 ,计算出时间序列的赫斯特指数、谱密度指数及其分形维数 ,发现各空间点测得的各物理量的归一化域值对时间具有标度性质 ,相对于均值的累积偏差曲线具有自仿射性 ,各物理量的时间序列彼此也具有自仿射性 ,其Hurst指数和分维数分别近似相等 .所得到的结果和前人用激光诱导荧光 (LIF)技术获取湍流 /非湍流界面图像而得到的结果一致 .

Dual Particle Dynamical Analyzer is used to measure the velocity and diameter at different spatial points in the spray zone of the process of air-blast nozzle atomization simultaneously.The so-called rescaled range analysis approach is used to study the time series of the velocity signals, diameters and transit times of droplets in the spray zone. According to the Hurst indexes and fractal dimensions computed from the time series, it has been found that, for any fixed spatial point, the normalized range of measured physical quantities possesses scaling property corresponding to time. Each curve of cumulative deviations relative to mean values is self-affine. The curves of different physical quantities are also self-affine with each other, since their Hurst indexes and fractal dimensions are identical approximately. The results obtained in this paper are consistent with those in the literature in which the turbulent/non-turbulent interface acquired by using the laser-induced fluorescence technique was reported.