An Improved LES Inflow Turbulence Boundary Condition Model And Its Application In Wind Effect Simulation Of High-rise Buildings

Large eddy simulation(LES)with high accuracy and providing high-resolution flow field space-time information is a current research hotspot in the field of computational wind engineering.Accurately simulating inflow turbulence is a prerequisite and indeed a great challenge in the numerical research of wind effects on building structures at current stage.In this paper,the basic theory and the current various inflow turbulence generators of LES were systematically summarized firstly.Then,an improved numerical model with self-sustained spatial correlation of LES inflow boundary condition was proposed,which bases on the newly proposed narrow band synthesis random flow generation(NSRFG)method.Then,LES simulation verification of the equilibrium atmospheric boundary layer(ABL)turbulent wind field was carried out,and a detailed study of flow around the CAARC standard high-rise building was conducted comprehensively.Finally,compared with the wind tunnel test,the numerical model was applied to simulation analysis of wind effects on the simplified models of an actual twin-tower ultra high-rise buildings.The work of this paper mainly includes the following aspects:(1)The basic theory and generation methods of LES inflow turbulence generator were comprehensively summarized,and the improved research based on the NSRFG method was carried out.Then,an improved inflow boundary condition numerical model-INSRFG method,was proposed to obtain the self-sustained spatial correlation,and a detailed theoretical derivation process was made to introduce the improved technology.Finally,the accuracy and reliability of INSRFG method of the inflow fluctuating wind generation were validated by numerical analysis.(2)Numerical simulation investigation of the turbulent wind field of the standard terrain of equilibrium ABL.The NSRFG LES method and the INSFRG LES method were used to study the three-dimensional fluctuation wind field of the four typical standard wind terrains defined in Chinese building code.The mean and fluctuating characteristics of the simulated turbulent wind fields by the two methods were then compared with the theoretical results extensively.The results show that the statistical characteristics of the turbulent wind field simulated by the two LES inflow turbulence generators can satisfy the requirements of CFD numerical simulation.Comparatively,the statistical characteristics of the ABL turbulent wind field generated by the INSFRG method,such as turbulence intensity,along-wind power spectrum,etc.,have relatively higher accuracy of the simulation results.(3)Large eddy simulation investigation of wind loads and wind-induced response of the CAARC standard building model.Three newly proposed LES inflow turbulence numerical models based on the turbulence synthesis method,the Consistent Discrete Random Inflow Generation(CDRFG)method proposed by the University of Western Ontario and the INSRFG and NSRFG methods proposed by the South China University of Technology respectively,were adopted here to simulate the three-dimensional unsteady fluctuation wind field of the turbulent flow around the CAARC standard building model.The mean and fluctuating wind pressure coefficient,spectrum of the base moments and non-Gaussian characteristics of turbulence characteristics by the three methods of the CAARC turbulent wind field,were compared and analyzed with the wind tunnel test in detail.Based on the wind tunnel test results,the applicability of three LES inflow turbulence generators in LES researches and the reliability and accuracy of INSFRG method are verified.Meanwhile,the numerical simulation results clearly describe the Gaussian characteristics of the fluctuating wind pressure on the windward side,as well as the Non-Gaussian characteristics of the crosswind and leeward side affected by the separation flow and wake.(4)Large eddy simulation investigation of wind effects and interference effects on the simplified models of an actual twin-tower ultra high-rise buildings in Wuhan.Based on a super high-rise building group project,the simplified numerical wind tunnel models of T3 and T4 office towers in the building group were established.Then,the three-dimensional unsteady flow around the towers under two working conditions was carried out using the INSFRG method and the NSRFG method,respectively.Compared with the wind tunnel test results,the mutual interference effects of wind effects on high-rise buildings were mainly discussed,and verified the applicability of the INSFRG method in engineering practice.