Numerical Simulation Analysis Of Wind Effects Of Configuration Details On Buildings

Wind effects on buildings and structures are mainly determined by means of field measurement, wind tunnel test, theoretical analysis and numerical simulations. With the development of computational technology, the numerical simulations, which are based on Computational Fluid Dynamics(CFD), have become more and more important in the field of wind engineering by its unique merits and promising prospect in the past three decades. In the background of engineering practice, this study focuses on the numerical simulations for the wind-resistant study of buildings and structures based on the FLUENT software. Meanwhile, the effects of configuration details on wind loads and wind field around buildings and bridge structures were discussed. The major contents of this paper are given as follows:Firstly, this paper is concerned with the unsteady characteristics of the conical vortex on a flat roof on the basis of numerical results by large eddy simulation(LES) under various terrain exposures for the wind direction of 45°. The results indicate that the LES can give fairly good results compared to the experimental pressure data of the AIJ flat roof model and other wind tunnel tests. Based on the Q criterion, this paper presents the flow visualization of conical vortices on the roof. By analyzing the mean and fluctuating pressure coefficients on the roof, it is observed that the strong suction acts on near leading edge of the flat roof, which is caused by a pair of conical vortices. In smooth flow, the strength of conical vortices is unbalanced in any time, when the strength of vortex recedes, the vortex on the other side is strengthened. But in the case of boundary-layer turbulent flow, this phenomenon was not recognized. By adding splitter plates and parapets, the LES results show that the alternative appearance of conical vortices may has inseparable relations with the interaction of vortices shed from the sidewalls of the building. The parapets can mitigate the high corner suctions on the roof and broaden the position of vortex core, while the dimension of conical vortex is greater with the higher parapets.Secondly, in order to study the effect of balconies on the wind loadings on buildings, a series of numerical simulations were conducted with LES in this paper. A flat roof building(breadth: depth: height=1.0:1.0:0.5) was considered in this study. By adding balconies to the facades of the building, the wind pressure distributions on the building and wind flow fields around the building for the cases with and without balconies were investigated. Different scenarios that affect the wind pressure distributions on the building were considered, such as approaching flow characteristics, wind direction(0°?15°?30°?45°) and the length of balconies. It is shown that the presence of balconies on the building can indeed lead to very strong changes in wind pressure distributions on windward facades, especially for the regions around the topmost row of balconies, because the balconies result in the changes of flow separation, recirculation and reattachment. In addition, the effect of balconies on the wind pressures on windward facades was strengthened with the increase of wind direction.Thirdly, a numerical approach based on Eulerian multiphase model is adopted to investigate the wind-driven rain(WDR) on bridge structures. Unlike existing methods, which are generally on the basis of Lagrange frame to deal with raindrop motions by trajectory-tracking techniques, the present approach considers both wind and rain motions as continuum under Euler frame. Then the WDR simulations for typical bridge decks and the North Bridge of Xiazhang Cross-sea Bridge in the Euler frame were realized by using User Defined Function of FLUENT software. The WDR parameters such as wind-driven rain field around bridge sectional model, catch ratio, rain-induced impact loads and the aerodynamic coefficients were obtained by the WDR simulations. Also, the effects of railings on wind field around bridge sectional model and the aerodynamic coefficients were investigated by numerical simulations of the rectangular and streamlined bridge sectional models. The results show that the impact of raindrops on the mean loads acting on the bridges is negligible and the changes of aerodynamic coefficients are small. The railings can weaken the rain-induced impact loads on the upper surface of deck and significantly change the wind field around bridge sectional model.Finally, the conclusions of this thesis and suggestions for further research were summarized, which are of great use for the wind-resistant study.