风与诱导气流协同影响半开放厂房扬尘的评估

Dust dispersion around a semi-open industrial building:assessing effects of wind and induced airflow

半开放厂房卸料时,矿料下落的诱导气流引起的扬尘在自然风作用下扩散,增加了厂房周围粉尘治理的难度。现有研究尚未对矿料下落时诱导气流和自然风共同作用扬尘扩散的影响进行定量分析。研究采用RNG k-ε模型建模探究在自然风作用下该类卸料时3种无量纲诱导流速对污染物扩散的影响。采用的模型及数值方法通过模拟结果与风洞试验结果对比吻合较好。结果表明卸料过程中不同诱导风速对半开放厂房背风面风速场影响不明显,但对背风面污染物浓度分布影响显著。特别在无量纲诱导流速高于0.4时,气流从料坑流向室外的区域接近一半,卸料侧的涡流区域扩大且在无量纲高度z/H为0.16处污染物浓度达到峰值。研究结果为工业园区半开放厂房卸料扬尘治理提供技术参考。

This study aims to evaluate the effects of the approaching wind and three different normalized induced airflow velocities(0.1,0.2 and 0.4)on the pollutant dispersion around a typical semi-open industrial building.The building is structured by three single buildings above the ground with the underground pits,respectively.The turbulence modelling approach with steady-state RNG k-ε model and numerical methods are carefully validated by comparing with two benchmark wind tunnel experiments,including wind around an isolated semi-open building,and another single building with a pollutant source.The approaching wind vertical profiles are inserted by the profiles of wind velocity,turbulent kinetic energy,and its dissipation rate,respectively.SIMPLEC algorithm is employed to solve the discretized equations and the second-order upwind scheme is selected for the convection and diffusion terms.The finite volume method is applied,and all the simulations are calculated until the residuals are below 10^(-5) for continuity,and 10^(-7) for the velocity components,kinetic energy,and dissipation rate.Results indicate that the simulated results give good agreement with the experimental results on the distributions of wind velocity and pollutant concentration.Furthermore,different induced airflow velocities give a slight effect on the flow patterns at the building leeward region,while they show a significant effect on the distributions of the normalized pollutant concentration.Turbulent kinetic energy has also been investigated on two measurement lines at the windward of the building and in the buildings,respectively.Note that the local turbulent kinetic energy increases with increasing the induced airflow velocity,which affects the pattern of pollutant dispersion both in and around the building.Specifically,there is a half area of induced airflow out of the pit when the normalized induced airflow velocity is above 0.4,together with the peak of the pollutant concentration at the plane Y=0 with the dimensionless height of 0.16.The aforementioned findings are helpful to the design and control of pollutant dispersion around the semi-open industrial building.