WSEAS Transactions on Fluid Mechanics
Print ISSN: 1790-5087, E-ISSN: 2224-347X
Volume 13, 2018
Building Generated Wind Shear and Turbulence Prediction Utilising Computational Fluid Dynamics
Author:
Abstract: Wind shear and turbulence caused by buildings in the vicinity of airports have been recognised as a cause of aircraft instability during landing or take-off for some time. The study of the pre and post-development winds has been undertaken using a quantitative Computational Fluid Dynamics (CFD) analysis. Turbulent (gust) wind flow in an urban environment is better modelled with wind tunnel when compared with CFD models employing low end turbulence models (e.g. the standard k-epsilon model). On the other hand small building features are better modelled in CFD versus wind tunnel testing, where model buildings are typically built to a scale of around 1:400 or 1:300. This is important when modelling small structures in the vicinity of airports or assessing the benefit of rounding the corners, adding small canopies, trees, porous screens and blades provided to mitigate adverse wind conditions. Wind tunnel measurements are also performed at a few selected points within the tested model while CFD can provide comprehensive output of the entire flow field. With advances in computational method Scale Resolving Simulation (SRS) models are used for high Reynolds number flows with strong separation. SRS models such as Large Eddy Simulation (LES) or hybrid LES/Reynolds Averaged Navier Stokes (RANS) approaches are used to overcome the limitation of statistical RANS models and resolve significant parts of the turbulence spectrum in CFD simulations. LES is still prohibitively computationally expensive when used for solving external high Re numbers flows in complex built environment even with today’s computational power. In this study hybrid Detached Eddy Simulation (DES) is used to assess the risks of buildings near the threshold of runways and predict wind shear and turbulence for critical flight paths. DES is proposed due to ability to combine the benefits of RANS and LES while minimising their disadvantages. The RANS (Realizable k-epsilon in this study) can achieve good prediction for attached boundary layers while LES can capture unsteady motions of large eddies in separated regions. The paper provides a procedure to reliably assess the risk of building generated wind shear and discusses some of the parameters that may have influence on the results accuracy.
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Pages: 126-135
WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 13, 2018, Art. #17