A Hybrid RANS and Kinematic Simulation of Wind Load Effects on Full-Scale Tall Buildings
Up till recent years, predicting wind loads on full-scale tall buildings using Large Eddy Simulation (LES) is still impractical due to a prohibitively large amount of meshes required, especially in the vicinity of the near-wall layers of the turbulent flo
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A Hybrid RANS and Kinematic Simulation of Wind Load Effects on Full-Scale Tall Buildings
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Introduction
In the design of increasingly taller and slender tall buildings, accurate predictions of spatiotemporally varying dynamic wind loads are the first necessary step. For the past several decades, wind tunnel testing has been the best practice to measure wind-induced load effects on tall buildings (Cermak 2003). By means of either the high-frequency force balance (HFFB) or synchronous multipressure sensing system (SMPSS), aerodynamic wind loads can be estimated experimentally on a rigid scaled model of the prototype. With the advent of computer technology, numerical simulations using computational fluid dynamics (CFD) techniques have been gradually gaining increased attention as an alternative approach for assessing wind effects on buildings (Senthooran et al. 2004; Huang et al. 2007; Tamura 2008). Much effort has been devoted to develop CFD techniques for analyzing turbulent flows around bluff bodies. Turbulence is a random fluid flow in which the velocity and pressure of the fluid fluctuate at random in both time and space. Theoretical and engineering computational models of turbulence have been developed to quantify the effect of turbulence fluctuations (Murakami 1997; Hanjalic and Kenjeres 2008). Most numerical turbulence models are involved in making approximations over spatial scales and temporal discretization scales. The Reynolds-averaged Navier– Stokes (RANS) simulation has been one of the successful CFD methods due to its efficiency and robust performance, especially with the development of various K e turbulence models (Murakami 1997), where the eddy viscosity is expressed as a function of turbulent kinetic energy K and the energy dissipation rate e. The RANS simulation is not a direct simulation of the turbulence, but only of its time-averaged statistics. Indeed, the significant accomplishment of RANS simulations is their ability to reliably predict the mean velocity and pressure fields of turbulent flows around a bluff body for engineering design purpose.
© Science Press and Springer Science+Business Media Singapore 2017 M. Huang, High-Rise Buildings Under Multi-Hazard Environment, DOI 10.1007/978-981-10-1744-5_3
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Various K e eddy viscosity turbulence models have been widely used in wind engineering applications, but the statistical ensemble-averaged turbulence models have difficulties in dealing with unsteady and non-stationary processes such as flow separation, reattachment, vortex-shedding behavior, and large-scale turbulent structures. More recently, time transient large eddy simulation (LES) has become a powerful CFD tool for turbulent flow analysis as it resolves the large-scale unsteady motions and accounts for smaller eddies using a subgrid-scale model (Rodi 1997; Tamura 2008). Unlike RANS using temporal averaging, LES employs spatial averaging over a spatial scale to filter smaller subgrid-scale eddies, but to retain the stochastic nature
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