标题： 淹没湍流射流外部边界的混合 显示英文标题

标题： Mixing at the external boundary of a submerged turbulent jet

摘要： 我们实验和理论上研究了淹没湍流射流外部边界的混合现象。 在实验研究中，我们使用粒子图像测速技术，并采用基于米氏散射强度分析的图像处理技术来确定示踪粒子的空间分布。 一股空气射流被香烟烟雾颗粒所标记，这些颗粒具有大的施密特数和小的斯托克斯数。 我们确定了由高浓度颗粒表征的射流流体和由低浓度示踪粒子表征的环境流体的空间分布。 在数据分析中，我们使用两种方法，其中一种方法基于测量的相函数，用于研究两种流体的混合状态。 另一种方法基于由湍流速度场对平均粒子数密度梯度的纠缠所产生的粒子数密度涨落的两点二阶相关函数的分析。 该梯度形成于淹没湍流射流的外部边界处。 我们证明了射流流体渗透到外部流动中的相函数的概率密度函数以及粒子数密度的两点二阶相关函数没有普遍的标度，不能用幂律函数描述。 本研究中的理论预测与获得的实验结果在定性上是一致的。 显示英文摘要

摘要： We study experimentally and theoretically mixing at the external boundary of a submerged turbulent jet. In the experimental study we use Particle Image Velocimetry and an Image Processing Technique based on the analysis of the intensity of the Mie scattering to determine the spatial distribution of tracer particles. An air jet is seeded with the incense smoke particles which are characterized by large Schmidt number and small Stokes number. We determine the spatial distributions of the jet fluid characterized by a high concentration of the particles and of the ambient fluid characterized by a low concentration of the tracer particles. In the data analysis we use two approaches, whereby one approach is based on the measured phase function for the study of the mixed state of two fluids. The other approach is based on the analysis of the two-point second-order correlation function of the particle number density fluctuations generated by tangling of the gradient of the mean particle number density by the turbulent velocity field. This gradient is formed at the external boundary of a submerged turbulent jet. We demonstrate that PDF of the phase function of a jet fluid penetrating into an external flow and the two-point second-order correlation function of the particle number density do not have universal scaling and cannot be described by a power-law function. The theoretical predictions made in this study are in a qualitative agreement with the obtained experimental results.