Numerical Investigation Of Wind Loads On High-rise Buildings Controlled By Suction/blowing

As a result of extensive utility of high-strength and light-weight materials in construction, high-rise buildings tend to be higher and more flexible, with a lower damping ratio. Therefore, they are very sensitive to the wind loads, and the wind-resistance design has gradually become the dominant factor in structural designs. Wind-resistance designs for high-rise buildings, including the aspects of strength, displacement and habitational comfort, are confronted with severe challenges under strong wind excitations, and the claddings frequently suffer from destruction, bringing substantial losses. Consequently, it is very important and necessary to investigate the numerical simulation techniques for analyzing the physical mechanisms of wind loads on high-rise buildings, and to take aerodynamic measures to reduce the wind loads and wind-induced responses.The flow control is a means to change the overall flowfield around bluff or streamlined body via using some locally aerodynamic measures, and its aim is to control the flow separation, improve the aerodynamic performance, reduce the drag and increase the lift-to-drag ratio for the airfoils. Actually, flow control is believed to be one of the most promising domains for research in the currently developed aerodynamics. In recent years, the active flow control techniques have become an increasingly attractive topic in fluid mechanics, and among them the suction or blowing method has already been widely used in domains of the aerospace, pipeline transportation and fluid machinery.In order to reduce the wind-induced drag and improve the wind-resistance performance of high-rise buildings, the continuous suction/blowing control method is introduced into the building structures. Based on verification and validation of the numerical methods by the experiment of suction/blowing control over the flow separation of a 3D backward-facing step, the Reynolds stress equation model (RSM) is used to investigate the performance of wind-load reduction for a high-rise building controlled by all-height or subsection suction/blowing on its side faces, and the mechanism of the wind-load reduction under suction/blowing control is clarified. Moreover, the"real"inflow turbulence in the atmosphere boundary layer is simulated, and the turbulence model of large eddy simulation (LES) is used to investigate the fluctuating wind loads on the rigid CAARC standard building model. Therefore, the numerical techniques for simulating the fluctuating wind loads on building structures are constructed.The main contents in the paper are shown as followings: 1. Three tuebulence models, including the Reynolds-averaged Navier-Stokes (RANS) method based on the RSM and the LES method based on the subgrid-scale stress models of the dynamic Smagorinsky-Lilly model (DSM) and dynamic kinetic energy subgrid-scale model (DKEM), are adopted to calculate flow separation of a 3D backward-facing step controlled by continuous suction/blowing, respectively. The numerical results are compared with the corresponding experiment data, and the credibility of using the RANS method based on the RSM and the LES method based on the DKEM to simulate separated flows around bluff body controlled by suction/blowing is validated. The CFD validation provides a solid foundation to correctly calculate the wind loads on a high-rise building controlled by continuous suction/blowing in the following paper.2. The performance of wind-load reduction for an all-height suction/blowing high-rise building is numerical investigated through the turbulence model of RSM. Effects of the orifice geometrical parameters and the suction/blowing flux parameters on the drag-reduction properties are analyzed, and detailed flowfields are showed to clarify the mechanism of suction/blowing control. Moreover, the power consumed and the counterforce induced by suction/blowing are discussed, and formulae for the coefficient of drag reduction (CDR) and the coefficient of along-wind base-moment reduction (CMR) are regressed, which can be referred for practical applications of the all-height suction/blowing high-rise buildings.3. In order to resolve the problems, such as installation of the suction/blowing equipments, continuous cooperations and functional usage of architectural space, induced by the all-height suction/blowing control on high-rise buildings, the performance of wind-load reduction for a high-rise building controlled by subsection suction/blowing along the height is numerical investigated through the turbulence model of RSM. The drag-reduction properties for the subsection and the all-height suction/blowing models are compared based on the maximal drag- reduction efficiencies and the minimal power consumed. Lastly, the formulae for the efficiency of drag reduction (ηDR) and the efficiency of along-wind base-moment reduction (ηMR) are regressed to be referred for practical applications of the subsection suction/blowing high-rise buildings.4. The similarities and differences between suction and blowing control to achieve the wind-load reduction for the high-rise building are compared based on the control principles, control parameters and control effects, and the feasibility of applying and implementing suction/blowing control for the wind-resistance design of high-rise buildings is discussed.5. Based on simulation of the"real"inflow turbulence in the atmosphere boundary layer, the LES method is used to investigate the characteristics of fluctuating wind loads on the CAARC standard building model, and effects of the influence parameters of numerical methods on the pressure coefficients, aerodynamic force/base-moment coefficients and power spectrum are analyzed. The numerical results are compared with the corresponding data from the wind tunnel tests, and the credibility of using the LES method together with the inflow turbulence boundary condition to simulate the fluctuating wind loads on bluff bodies in the atmosphere boundary layer is validated. Based on the studies, the ultimate aim is to investigate the fluctuating wind loads and characteristics of the crosswind vortex shedding for the suction/blowing controlled high-rise buildings in the future work.