城市主城区立体模型的构建与风环境模拟——以广州主城区为例

Construction of the three⁃dimensional model and simulation of the wind field in central urban districts:A case study of Guangzhou central urban districts

以22 km×21 km的广州主城区为例,以40 m建筑间距作为风道宽度低限、用容积高度对建筑高度赋值和垂向拔高为建模特色,概括构建了城市尺度的立体模型。在此基础上,分别模拟了广州主城区中性流条件下,弱风(2 m/s)和强风(5 m/s)、近地面10、25、50 m三个高度的风环境。模拟表明:来流5 m/s下主城区存在不同风速等级、不同平面形态以及不同高度面的风道;白云山、珠江新城等面积较大的地形或建筑高地形成了减速明显的背风区条带,并相互组合形成了重要的风口和具有较高基面的强风道;在不同高度上主城区风速均由周边向城市中心降低;风道风速强烈地依赖于风道走向,风道风速与走向夹角呈三次函数递减,两者拟合优度R2为0.512。模拟结果很好地呈现了城市尺度宏观地形白云山和建筑密集区相互间的作用,反映了城市尺度模型构建与模拟的优势。

An urban⁃scale three⁃dimensional model is constructed based on the workstation platform,and the method of CFD is used to simulate the urban wind environment under the condition of neutral current and identify ventilation channels on different spatial scales,which will help to enrich the methods and theories of ventilation channels planning.Through combining the generalized construction of the urban⁃scale three⁃dimensional shape with the identification of ventilation channels organically,this paper takes 22×21 km of main urban area of Guangzhou as an example,takes 40 m of building spacing as the low limit of wind tunnel width,uses the volume height to assign the building height and vertical elevation as the modeling characteristics,and builds a simplified and generalized three⁃dimensional model of urban scale.The wind environment near the ground at the height of 10 m and 25 m under the condition of neutral current in Guangzhou central urban districts is simulated under different combinations of weak wind(2 m/s)and prevailing wind(5 m/s)and southeast and northwest wind directions through the process of urban⁃scale three⁃dimensional modeling,grid division,calculation and solution.The simulation shows that:whether it is weak wind or prevailing wind,there exist ventilation channels with different wind speed levels,different plane shapes and different height surfaces in central urban districts;large terrains or building highlands such as Baiyun Mountain and Pearl River New Town form obviously leeward area with obvious decreasing speed,which combine with each other to form important vents and strong ventilation channels with higher bottom surfaces.The wind speed in Guangzhou decreases from the periphery to the city center at different heights averagely.The wind speed and direction of the downwind ventilation channel under the northwest wind and north wind decrease in cubic function.The simulation results show the interaction between Baiyun Mountain and dense building areas on a macro⁃scale and reflect the advantages of urban⁃scale model construction and simulation.Meanwhile,it shows that the technical route of constructing urban⁃scale three⁃dimensional model and simulation for the method of CFD based on workstation is simple and feasible.