Numerical Simulation Study Of Complex Tree-shaped Stuructures And The Windbreak Performance Of The Trees

People tend to improve the surrounding wind and thermal environment by planting trees. When wind passes through the trees, the energy and speed of it gradually reduce, while the turbulence intensity increases in the downstream area. However, the effects of trees on the wind load of nearby buildings were often ignored in the previous studies of structural wind engineering. Instead, they were considered in respect of site classifications. It is reasonable for super tall building and large-span roof structure. In terms of low-rise buildings, the influences of the trees cannot be ignored, especially when the surrounding trees and the low-rise building are close enough and have a similar height. Likewise, the existence of trees has certain influences on the wind environment of group buildings. Given this condition, it is necessary for researchers to adopt proper means to study the windbreak performance of trees. Firstly, this paper discusses the accuracy and validity of CFD numerical simulation method in practical engineering applications by simulating a complex tree-shaped structure. Secondly, the application of windbreak performance of trees in structural wind engineering is investigated systematically.Taking huafa art museum in Zhuhai as the engineering background, comparative study of the complex tree-shaped structures between wind tunnel test and CFD numerical simulation is undertaken. In the simulation, the wind pressure distributions on the tree crown of two typical tree structures are mainly studied. It turns out that the numerical simulation can accurately predict the wind pressure distributions on the complex structures. The wind pressure distribution on each tree crown is mostly interfered by neighboring tree structures and the museum. Meanwhile, the wind environment of the museum is researched combining with the meteorological data in Zhuhai. According to the result, the wind environment in the museum is in good condition, although the wind speed ratio in some regions is comparatively bigger because of the channeling effect.In order to study the windbreak performance of trees on low-rise buildings, the method of compiling UDF is adopted. By changing additional source in momentum, turbulent energy and turbulent dissipation equations with this method, the wind flow around effect is simulated. The result indicates that the flow around effect can be satisfactorily evaluated by the method of adding additional source, in spite of a few deviations in some downstream regions of the trees. Meanwhile, by changing the distance between the low-rise building and the tree groups, the height and porosity of the trees, the influences of the windbreak performance of trees on low-rise buildings are studied systematically. It turns out that the influences are bigger in the windward regions than that in the leeward regions. From the respect of roofing division, the influences in the region of roof ridge are smaller than that in other regions. In general, the windbreak performance of trees on low-rise buildings is highly distinct, and it can contribute significantly to the reduction of wind loads on the roof.This paper numerically simulates the wind environment of a typical high-rise residential building. The wind environment in this district is optimized by the means of planting trees. In the simulation process, the trees are defined as porous media to reduce the difficulty in dividing mesh. It is concluded that the existence of trees complicates the airflow in the residential district within a rational range. And it also reduces the area of strong wind in pedestrian passage, so as to achieve the purpose of improving the wind environment.Finally, the conclusions of this thesis and suggestions for further research are summarized, which are of great use for the wind-resistant design in practical engineering.