CFD Simulation Of Urban Space Wind Field Based On Detached Eddy Simulation Method

In recent years,a large number of skyscrapers have appeared in coastal area of China.These buildings are like a screen of city,blocking natural winds and inflows,causing regional air pollution problems.In a complex system such as the urban wind farm,the influence of such a special architectural form of the screen building on the urban space wind field requires us to pay attention to it.Detach ed Eddy Simulation(DES),as a new turbulent numerical simulation method,has its own unique advantages.However,at present,the application of DES in the study of wind fields,especially urban wind fields,is not common and deserves further study.Therefore,based on the DES,this thesis analyzes the influence of different building forms on the wind field around the building,and attempts to apply the DES to the complex field model,and analyzes the wind field around the special building in the field model.Based on the classical flow model about flow around a square column,the DES method with the best simulation efficiency and precision in the flow characteristics and aerodynamic characteristics in the flow field is determined.In this paper,the simulation results of SA-DES,SA-DDES,SST k-? DES and LES based on smagorinsky were carried by OpenFOAM which is an open source CFD software.And compared the results with the classical mechanical experiment and simulation done by other scholars.The results show that SST k-? DES is the best in the simulation of the three vortex separation methods,and it is more efficient than the LES method.Using SST k-? DES method to figure out the morphological characteristic of buildings that have a dramatic impact on the flow field around the building.Firstly,based on the wind tunnel test results,the accuracy of simulation results of DES method are evaluated.The results show that the accuracy of simulation and calculation efficiency of DES are up to exception.The ana lysis results show that the thickness of the building has little effect on the surrounding flow field.The larger the value of the windward surface height and the windward surface width,the larger the wind speed increasing area appears around the building.In addition,the increase in the width of the windward side simultaneously expands the area of the low wind speed zone downstream of the building to varying degrees.The DES is used to simulate and analyze the wind direction of urban areas with complex terrain and buildings.It is found that under the wind direction of 90 °and 120 °,the target building will have a severe effect on the surrounding flow field after the completion of the building.There are significant changes in the mean and instantaneous wind speeds at the monitoring points.At the same time,through the analysis of the wind field around several typical screen towers in the urban area,it is found that there are high wind speed areas in the corners and low wind speed areas in the lower reaches,which verifies the conclusions of the previous numerical simulation and wind tunnel tests.The extreme shape of the screen floor makes the surrounding wind field difficult to predict and seriously affects the living and health of the surrounding residents.The CFD simulation of urban wind environment can effectively reflect the complex wind field distribution in urban area.The DES method provides a new simulation method with both efficiency and precision for urban spatial wind field,and it has important practical application value.