Numerical simulation of the wind flow around a tall building and its dynamic response to wind excitation

Wind action is particularly important for tall buildings, both in providing a significant contribution to the dynamic overall loading on the structure and by affecting its serviceability. Whereas low and medium-rise buildings are fairly rigid, tall structures are characterized by a greater flexibility and a lower natural frequency, which is more likely to be in the frequency range of wind gusts. In addition, wake effects, such as vortex shedding, can become a significant problem for flexible structures when the vortex shedding frequency is close to the natural frequency of the building. The aim of the present thesis is to assess the validity of commercial CFD codes for modelling the wind flow around a high-rise building, including the consideration of the coupled dynamic response of the building to turbulent wind loading. Three intermediate objectives are set. The first is to develop a tool to couple fluid and structure in a sequential manner. The equations for the air flow are solved using the commercial CFD program ANSYS-Fluent. The response of the structure is found from solving the structural response with a modal approach, the response in each vibration mode being treated as a SDOF problem. This fluid-structure interaction tool is applied to model a 180 m building, allowed to move in the across wind direction. The second objective is to investigate and find a method to generate fully turbulent inflow for LES in order to reproduce an accurate wind spectrum. The chosen method is tested and validated in an empty fetch. Ultimately, both tools are brought together and applied to model a 180 m building, which is allowed to bend in the along wind and across wind directions. Finally, the third intermediate objective brings together the tools developed in the first and second intermediate objective to model the dynamic response of a 180 m building to dynamic wind loading, within a turbulent inflow, using LES.