A Simplified Method For The Model Of Building Groups In CFD Simulation Of Urban Wind Environment

With the rapid development of China's urbanization process,there appears the negative impact of urbanization on the ecological environment in Chinese cities.Urban wind environment is the condition of wind flow in the urban area,good wind environment in urban areas has significant effect on the solution of urban diseases such as urban heat island effect,the pollutant diffusion,building energy conservation etc.,so the planning of wind environment has received the attention of scholars.As a numerical simulation technique,CFD(Computational Fluid Dynamics)provides a new solution for the simulation analysis of urban wind environment,which could assist urban wind environment design in the planning stage.However,the CFD simulation of wind environment in large-scale urban area consumes a lot of computing resources with high computing cost and low efficiency.To improve the efficiency of CFD simulation,it is necessary to simplify the geometry models reasonably of building groups in urban area.This study proposes a simplified method for the model of building groups in CFD simulation,aiming at reducing computational complexity,promoting the application of CFD in urban wind environment simulation.First of all,this study simplified the actual layout of buildings which is the key factor that influences the wind environment around buildings,the ideal model was set up and four control parameters(B/L,W/L,H/L and D/L,the ratio of the building interval B,the building width W,the building height H and the offset distance of central axis of building D to the building length L)were selected as the reference of the simplification.After that,this study applied two experiment methods(the single factor experiment and the orthogonal experiment)and CFD software to explore the influence of each control parameter on the results of simplification.The experiment results showed that the influence degree of each control parameter on the flow field velocity change caused by the simplification of the building model is D/L>B/L>H/L>W/L,further a control index(the reasonable value range of four control parameters)was obtained as a reference for the simplification of the model of building groups: B/L?[0.0,1.5],W/L?[0.0,2.0],D/L?[0.0,0.25],H/L?[0.0,1.0],Finally,a case study was conducted on the building groups of Tsinghua University in Beijing,the condition of wind environment before and after the simplification was analyzed,which verified the effectiveness of the simplified method and the control index.The simplified method of building groups mentioned in this study can reduce the number of grids and improve the quality of grids in CFD simulation,that means we can improve the computational efficiency while ensure reliable calculation results,which is beneficial to the effective implementation of CFD in large-scale urban wind environment simulation.