Similar Simulation Study Of Atmospheric Flow In Urban Environment

With the continuous improvement of CFD numerical simulation technology,more and more researchers apply CFD technology to the research of urban microclimate.However,the accuracy of CFD numerical simulation depends on the turbulence simulation method and the discrete density of the grid.It has high requirements on computer hardware.It is difficult for general performance computers to meet the memory and storage requirements of urban microclimate numerical simulation,which will limit the average scholars for CFD technology.In this paper,the scale model based on similarity theory is used to simulate the real city microclimate,which ensures the similarity between the scale model and the real phenomenon.The method can reduce the number of computing grids to a certain extent,thereby effectively reducing the requirements on computer memory and storage conditions,and providing a possible method for solving the above problems.The verification of the CFD scale simulation method is based on the Reynolds average governing equations which respectively based on the background conditions of neutral atmospheric flow and buoyancy affecting atmospheric flow,using the equation derivation method to derive the similarity criterions between the full-scale model and the scale model.By controlling the principle of consistency of similarity rules of the same name,the boundary conditions of the similarity of the scale model and the physical performance parameters of the virtual flow medium are derived;Based on the Fluent 17.0 platform,the model and the scale one are numerically simulated.By comparing the simulation results of the atmospheric flow around the two models' buildings,the research is analyzed from the three aspects of the authenticity,accuracy and effectiveness of the simulation,and the following conclusions are drawn:1.Background conditions based on neutral atmospheric flow:(1)The scale model based on similarity theory can reproduce the flow pattern of the full-scale model in the plane position and vertical position to achieve the phenomenon similarity.(2)The scale simulation has high precision.The dimensionless results of the full-scale model and the scale model are best suited for high wind speed areas on the downwind and the windward side of the building.Howere,there will be some error in the region of low wind speed like the vortex region,which also shows that increasing the Reynolds number can improve the simulation accuracy of the scale simulation.(3)By comparing the calculation time between the two models under the same conditions,the scale model can effectively improve the calculationefficiency compared with the full-scale model.2.Background conditions based on atmospheric flow considering the buoyancy affecting:(1)The scale model based on similarity theory can reproduce the flow pattern of the full-scale model in the plane position and vertical position to achieve the phenomenon similarity.(2)The scale simulation has high precision.The dimensionless results of the full-scale model and the scale model are best suited for high wind speed areas on the downwind and the windward side of the building.However,there will be a certain degree of error in the region of low wind speed like the vortex region and the region where the temperature difference varies greatly like the area near the wall.It also shows that the Reynolds number and the Richardson number will affect the simulation accuracy of the scale simulation.(3)By comparing the calculation time between the two models under the same conditions,the scale model can effectively improve the calculation efficiency compared with the full-scale model.