Numerical Aero-elastic Analysis Of Tall Flexible Building By Various Turbulent Inflow Generation Methods

With the development of science and technology,the height of tall buildings is increasing.As the tall buildings have the inherent characteristics in high flexibility light-weighted and small damping ratio,the effect of wind loading on such tall buildings is more obvious.To accurately control the influence of the wind loading on the safety and comfortability of tall buildings,and provide accurate data for the wind-resistant design of tall building structures,Computational Fluid Dynamics(CFD)numerical simulation on wind loading has become one of the most important research methods.In that,Large Eddy Simulation(LES)is an important method to study turbulent effect on tall buildings in wind engineering.The turbulent inflow methods for Large Eddy Simulation is studied in this dissertation.A linear filtration method to generate the time history anisotropic fluctuating wind field was proposed.Numerical analysis procedure of wind loading and its response on CAARC model was also introduced.A technical scheme for Fluid Structure Interaction(FSI)is briefly described.The main research contents of this dissertation are as follows:(1)The basic theory of atmospheric boundary layer and numerical simulation on wind loading on buildings are first introduced.The governing equations of CFD is briefly introduced.Then the characteristics of wind field in the atmospheric boundary layer are studied.The mean wind speed,turbulence intensity,turbulence integral scale and Reynolds stress in wind field which need to be taken into consideration are explained in detail.(2)A Linear Filtering(LF)method is proposed to generate turbulent wind field.The procedure for the proposed simulation algorithm is elaborated.The treatment on how to satisfy time and space correlation of the simulated wind field is then discussed.A suitable random number generation method is proposed to satisfy the randomness of fluctuation.Based on the simulated turbulence inflow,a Large Eddy Simulation method is utilized to simulate the wind loading on the surface of CAARC building model.The mean wind pressure coefficient is found to be close to the experimental data.The normalized power spectral densities of along-wind,cross-wind and torsional moment at six different levels of CAARC building are investigated.That the simulated vortex structures around the building shows that the turbulent wind field obtained by this method is in good agreement with the reality.(3)A standard k-ε turbulence model is also utilized for obtaining unsteady wind loading on CARRC building for comparing purpose.The mean and fluctuating wind pressure coefficient,and normalized power spectral densities of along-wind,cross-wind and torsional moment at six different levels of CAARC building are also obtained investigated and compared with those results from LES model.It is found that results from LES model is more accurate than those from k-ε model.For the normalized Power Spectral Densities(PSD)of along-wind,cross-wind and torsional moment at different levels,the PSD cures for cross-wind and torsional moment are similar,but some difference occurs at the along-wind curve.(4)A schemes for Fluid Structure Interaction(FSI),which are hooked by Fluent 14 through User Defined Function(UDF)was designed in this dissertation.The Arbitrary Lagrangian Eulerian(ALE)dynamic mesh around the building model is constructed by hexahedral meshes for obtaining quick convergence and high precision in CFD numerical simulation.Wind loading and wind-induced response on CAARC building model is conducted by LES method combined with Discretizing and Synthesizing Random Flow Generation(DSRFG)turbulent inflow generating scheme.Numerical analysis results from both rigid building model and flexible building model are conducted and compared by the proposed methodology.Compared results show that the distribution of mean wind pressure distributions and normalized power spectral densities of along-wind,cross-wind from two types of building model are similar.However some difference exist in the PSD cure for the torsional moment.It is possible that along wind loading could affect the torque moment in the flexible model.Compared results show that the proposed FSI scheme is generally effective to obtain the CFD numerical analyzed wind loading of tall flexible buildings.