Abstract
This study is aimed at developing a novel computational framework that can essentially simulate a tornadic wind field and investigate the wind loadings on ground constructions. It is well known that tornado is a highly turbulent airflow that simultaneously translates, rotates and updrafts with a high speed. Tornadoes induce a significantly elevated level of wind forces if compared to a straight-line wind. A suitably designed building for a straight-line wind would fail to survive when exposed to a tornadic-like wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. Since the study of tornado dynamics relying on field observations and laboratory experiments is usually expensive, restrictive, and time-consuming, computer simulation mainly via the large eddy simulation (LES) method has become a more attractive research direction in shedding light on the intricate characteristics of a tornadic wind field. For numerical simulation of a tornado-building interaction scenario, it looks quite challenging to seek a set of physically-rational and meanwhile computationally-practical boundary conditions to accompany traditional CFD approaches; however, little literature can be found, as of today, in three-dimensional (3D) computational tornado dynamics study. Inspired by the development of the immersed boundary (IB) method, this study employed a re-tailored Rankine-combined vortex model (RCVM) that applies the “relative motion” principle to the translational component of tornado, such that the building is viewed as “virtually” translating towards a “pinned” rotational flow that remains time-invariant at the far field region. This revision renders a steady-state kinematic condition applicable to the outer boundary of a large tornado simulation domain, successfully circumventing the boundary condition updating process that the original RCVM would have to suffer, and tremendously accelerating the computation. Wind loading and its influence factors are comprehensively investigated and analyzed both on a single building and on a multiple-building configuration. The relation between the wind loadings and the height and shape of the building is also examined in detail. Knowledge of these loadings may lead to design strategies that can enable ground construction to be more resistant to tornadoes, reducing the losses caused by this type of disastrous weather.
Highlights
1.1 Background and motivationTornadoes are more frequently reported in Canada than any other country except the United States
The classical Rankine-Combined Vortex Model (RCVM) is re-tailored so that an 50 immersed boundary (IB) lattice Boltzmann method (LBM) can be handily applied to the investigation of the tornado-construction interaction mechanism, and this hybrid framework has been enriched by the sub-grid stress (SGS) model, so that the simulation of a tornado-building interaction scenario at an elevated Reynolds number (Re) becomes manageable with ease
The effectiveness of the present immersed boundary-Lattice Boltzmann Method (IB-LBM) computational framework with the re-tailored Rankine-combined vortex model (RCVM) embedded is demonstrated through the validating cases in which the IB-LBM results respectively for translational and rotational flows are found in good agreement with the simulation data obtained elsewhere using other numerical approaches
Summary
1.1 Background and motivationTornadoes are more frequently reported in Canada than any other country except the United States. A properly designed model for a straight-line wind would fail to describe a tornado-like wind even if the two winds have the same translational speed [25]. This is because a tornado can be essentially decomposed into simultaneous translational and rotational flow components, and both have to be considered in the model for a tornado. A well-established tornado model has always been sought, since it would help the researchers better understand, through economical computer-aided simulations, the tornado dynamics as well as the mechanism of tornado-building interaction and, improve the design of buildings towards their enhanced wind-resistant capabilities. A time-independence form of boundary condition was set up, and the original highly time-dependent model can be completely converted as a traditional moving boundary problem, which was solved with IBM efficiently and straightforwardly
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