基于多相质点网格法的大气污染仿真模拟

A Simulation of Atmospheric Pollution Based on Multi-phase Particle-in-cell Method

为了准确估计不同风速条件对单点源排放的污染物浓度时空分布、粒子抬升高度、污染物扩散范围产生的影响,使用以多相质点网格(multi-phase particle-in-cell,MP-PIC)方法为基础的拉格朗日粒子追踪模型对污染物扩散进行大涡仿真模拟。结果表明:低风速下,受污染源阻挡作用,污染源周边形成方柱绕流现象,污染物在下风方向分裂为两股,污染物随湍流作用在计算域内波动,且计算域内分裂状况始终存在。随着风速的增大,污染物分裂情况逐渐消失,且污染物扩散范围、粒子最大抬升高度随风速增大而减小。风速为2 m/s时,分裂的两股污染物之间距离为5~20 m,流场稳定时下风向1000~1300 m污染物最大数浓度为70~87个/m^3;风速为5 m/s时,分裂的两股污染物距离为2~10 m,流场稳定时下风向1000~1300 m污染物最大数浓度为212~300个/m^3;风速为10 m/s时,分裂情况消失,流场稳定时下风向1000~1300 m污染物最大数浓度为407~502个/m^3。

In order to study the spatial and temporal distribution of pollutants as well as the elevated height of the particle,and the distance of pollutant diffusion under different wind speed conditions,a lagrangian particle tracking model based on multi-phase particle-in-cell(MP-PIC)was used to capture the diffusion of contaminants.The results show that the flow around a square cylinder occursat low wind speed due to the blocking effect of pollution sources.Moreover,pollutants are split into two groups along the downwind direction.The pollutants fluctuate in the computational domain under the influence of turbulence,and the splitting is lasting in the computational domain.When the wind speed is 2 m/s,the distance between the splitting groups is 5 to 20 m,and the maximum number concentration of pollutants is 70 m^-3 to 87 m^-3 along the downwind direction from 1000 m to 1300 m.When the wind speed increases to 5 m/s,the distance between these two pollutants groups is 2~10 m.When the flow field becomes steady,the maximum number concentration of pollutants along the downwind direction from 1000 m to 1300 m is 212 m^-3 to 300 m^-3.When the wind speed is 10 m/s,the splitting phenomenon disappears,and the maximum number concentration of pollutants along the downwind direction from 1000 m to 1300 m becomes 407 m^-3 to 502 m^-3.