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

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.