Numerical Study On Pollutant Dispersion Between Adjacent Industrial Buildings Under Natural Ventilation

Natural ventilation of buildings is the flow generated by temperature differences and by the wind.The governing feature of this flow is the exchange between an interior space and the external ambient.Natural ventilation has the advantages of a large ventilation flow rate and zero energy consumption.And Natural ventilation is a suitable form of ventilation which is often used in industrial workshops with high intensity heat sources and pollution sources indoors,because such workshops require large amounts of ventilation.However,it also has many weaknesses,such as the lack of pre-treatment ability of supply air temperature,humidity and air cleanliness,and the lack of ability to accurately adjust the ventilation volume.More importantly,there are usually pollution sources inside industrial workshops,which are accompanied by the diffusion of pollutants under natural ventilation.At the same time,the layout of industrial workshops is tight,and while pollutants spread to the outdoor environment and stay in the external space of adjacent buildings,they may also enter adjacent buildings again.In this study,a two-dimensional numerical simulation of the diffusion of pollutants between two adjacent industrial workshops is carried out.Firstly,the relevant literature is consulted according to the specific issues involved in this study,and the data in the literature is used to verify the accuracy of numerical methods used in this article.Secondly,the characteristics of the flow field of the building space composed of two adjacent industrial buildings under different incoming wind speeds are studied,and the critical Reynolds number(Re)when the air flow structure reached independence is determined(Re _H=31965).Finally,under the wind speed that meets the requirement of Reynolds number independence,a steady-state simulation of pollutants dispersion in the adjacent building environment is carried out,focusing on the influence of indoor thermal intensity,window opening conditions,and building canyon aspect ratio factors on the air flow around the workshop and the diffusion of pollutants.The conclusions are as follows:(1)When the pollutants released from the upstream workshop spread downwind,there is a significant interaction between the wind and buoyancy generated by the downstream workshop’s heat source.And this relationship can be evaluated using the Richardson number(Ri).The ventilation direction of the downstream workshop is affected by the Richardson number.When Ri<1.6,the airflow is mainly driven by wind,which flows from the leeward of the downstream workshop to the street canyon.When Ri>1.6,buoyancy’s effect begins non-negligible,the ventilation of the downstream workshop comes from the street canyon.There is a low concentration of the pedestrian breathing area and downstream workshop,when the airflow is driven by wind.When the airflow is driven by buoyancy,the pollutants migrate to the pedestrian breathing area and the downstream workshop.(2)The window opening conditions for pollutants to spread to the upstream workshop in the upwind direction have been determined.Only when the leeward window of the upstream workshop and the windward window of the downstream workshop are opened at the same time,the pollutants released by the downstream workshop will spread into the upstream workshop.And when the downstream workshop uses windward windows for unilateral ventilation,the building canyon and upstream workshop has the largest pollutant concentration.There is an exponentially increasing relationship between the aspect ratio of the building canyon and pollutants concentration in the building canyon and the upstream workshop.