混合颗粒点源扩散风洞试验研究

Wind tunnel dispersion experiment on mixed sand particles from a point source

针对沙尘的扩散问题开展了沙粒点源扩散风洞实验,结果显示沙粒经点源扩散后质量沿高度的分布服从高斯分布,这与已有点源扩散研究结果一致.随着风速的变化,沙粒垂向扩散的中心高度随风速的平方呈反比,均方差随风速呈反比;随着与点源距离的增加,中心高度呈线性减小,均方差呈线性增加.同时,根据实验结果给出了点源扩散分布质量沿高度分布的中心高度和均方差随风速、粒径和扩散距离的表征方程.此外,分析结果还表明混合沙粒扩散后不同高度处的平均粒径随高度呈线性递减,这与已有的野外沙尘暴期间的粉尘粒径观测结果是一致的.

The motion of particles, such as dispersion of dust and volcanic ash, in the atmosphere can lead to various environmental problems and endanger our daily life. In the paper, a dispersion experiment of mixed sand particles from a point source in wind tunnel was performed to enhance our understanding of the dynamics of sand particles in the atmosphere. The results revealed that the mass distribution of dispersed particles from the source point followed the Gaussian law at the vertical direction, which is consistent with previous studies. The Gauss mean value of dispersed particles was inversely proportional to the square of the friction speed, but decreased linearly with the distance of the dispersion downwind being away from the source point. In contrast, the mean square deviation was inversely proportional to the friction speed, and increased linearly with the distance of dispersion. Based on the experimental results, both the Gauss mean value and the mean square deviation were related to wind velocity, the averaged diameter of particles and the distance of dispersion, and explicit expressions were obtained correspondingly. Furthermore, the averaged diameter of dispersed particles along height at the vertical direction was analyzed and the results showed the averaged diameter decreased linearly with the height, which is in accordance with the observed results in the field during dust storms.