Similarity principle of particulate dispersion between wind tunnel and atmospheric boundary layer: A combined theoretical and experimental study

Understanding the dispersion behaviors of radioactive particles in the atmospheric boundary layer is critical for assessing their environmental impact from nuclear facility emissions. Wind tunnels have been extensively employed to investigate wind field characteristics and atmospheric dispersion behavior of particles based on scaled similarity principles. Nevertheless, quantitative criteria governing particles similarity between wind tunnel and real atmospheric boundary layer remains largely unexplored. Here, a coupled computational fluid dynamics and discrete particle model approach was employed to quantify particles concentration distribution validated by wind tunnel experiments. Quantitative validation results revealed remarkable consistency between optimized numerical model and wind tunnel experiments for particles with three different diameters. More importantly, a similarity principle governing particles dispersion between wind tunnel and real atmospheric boundary layer environment was established via comprehensive quantitative comparison of dimensionless concentration fields. This principle revealed the scaling ratio of particle aerodynamic diameter is proportional to the one-sixth power of the spatial scale ratio when performing the wind tunnel particle dispersion experiment. Further discussion showed wind velocity has no obvious effect on the similarity principle of particles. Besides, the sphericality of particles would have an impact on the similarity principle for large size particles. This study provides fundamental data to validate particles dispersion model and guidelines to perform particle dispersion experiment in the wind tunnel system.