Simplified Wind Flow Model for the Estimation of Aerodynamic Effects on Small Structures

The reliable measurement of pressures on low-rise buildings in the atmospheric boundary layer (ABL) flow remains a challenge, as hasbeenshownbythelargediscrepanciesamongresultsobtainedindifferentwindtunnelfacilitiesoreveninthesamewindtunnel.Twomajor causes of the discrepancies are the difficulty of simulating large-scale, low-frequency turbulent fluctuations uniformly across laboratories and the small scale of models in typical civil engineering wind tunnels. To address these issues, it was proposed that a simplified flow be used in laboratory simulations,rather thana conventionalABL flow.In thesimplified flowthe referencemeanwind speedislarger thanthemean wind speed of the ABL flow, and the low-frequency fluctuations present in the ABL flow are suppressed; that is, the peak energy of the missing low- frequency fluctuations is supplied in the simplified flow by the increment in the mean wind speed, which may be regarded as a flow fluctuation with zero frequency. High-frequency turbulent fluctuations, which typically affect flow reattachment, are approximately the same in the ABL and the simplified flow. Because, over small distances, low-frequency fluctuations are highly coherent spatially for small low-rise buildings with dimensions of up to approximately 20 m (e.g., single-family residential homes), the peak aerodynamic effects of the two flows may be hypothesized to be approximately the same. Preliminary experimental results obtained in University of Western Ontario's ABL wind tunnel facility and Florida International University's small-scale Wall of Wind facility are shown to support this hypothesis. The use of the proposed simplified flow is currently being tested by the authors for application to computational wind engineering (CWE) applications. Such use eliminatestheneedtosimulatethelowerfrequency fluctuationsoftheboundarylayer flowandthusmakesitpossibletoachievepracticalCWE calculations, and it is advantageous in experiments from the points of view of measurement accuracy, model scaling, repeatability of the simulations, and computational efficiency. DOI: 10.1061/(ASCE)EM.1943-7889.0000508. © 2013 American Society of Civil Engineers. CE Database subject headings: Boundary layers; Wind loads; Low-rise buildings; Wind tunnels. Author keywords: Atmospheric boundary layer; Computational wind engineering; Flow modeling; Low-rise buildings; Wind engineering; Wind tunnel tests.

[1]  Fahim Sadek,et al.  Peak Non-Gaussian Wind Effects for Database-Assisted Low-Rise Building Design , 2002 .

[2]  David Banks,et al.  A model of roof-top surface pressures produced by conical vortices:Evaluation and implications , 2001 .

[3]  N. Isyumov,et al.  Wind pressures acting on low-rise buildings , 1999 .

[4]  Chris Letchford,et al.  International Comparison of Wind Tunnel Estimates of Wind Effects on Low-Rise Buildings: Test-Related Uncertainties , 2008 .

[5]  N. Null.  Minimum Design Loads for Buildings and Other Structures , 2003 .

[6]  H. Tieleman.  Wind tunnel simulation of wind loading on low-rise structures: a review , 2003 .

[7]  G. Kopp,et al.  The UWO contribution to the NIST aerodynamic database for wind loads on low buildings: Part 2. Comparison of data with wind load provisions , 2005 .

[8]  Joseph A. Main,et al.  Comparative Inter-Laboratory Study of Wind Loading on Low Industrial Buildings , 2007 .

[9]  A G Davenport,et al.  NOTE ON THE DISTRIBUTION OF THE LARGEST VALUE OF A RANDOM FUNCTION WITH APPLICATION TO GUST LOADING. , 1964 .

[10]  Edward Cohen,et al.  Minimum Design Loads for Buildings and Other Structures , 1990 .

[11]  Arindam Gan Chowdhury,et al.  Development of devices and methods for simulation of hurricane winds in a full-scale testing facility , 2009 .

[12]  Theodore Stathopoulos,et al.  Wind loads on low buildings: in the wake of Alan Davenport's contributions , 2003 .

[13]  Joseph A. Main,et al.  Wind Effects on Low-Rise Buildings : Database-Assisted Design vs . ASCE 705 Standard Estimates , 2008 .

[14]  Arindam Gan Chowdhury,et al.  A proposed technique for determining aerodynamic pressures on residential homes , 2012 .

[15]  Arindam Gan Chowdhury,et al.  Wind profile management and blockage assessment for a new 12-fan Wall of Wind facility at FIU , 2011 .

[16]  Joseph A. Main,et al.  Wind Effects on Low-Rise Metal Buildings: Database-Assisted Design versus ASCE 7-05 Standard Estimates , 2010 .

[17]  Emil Simiu,et al.  Design of Buildings for Wind: A Guide for ASCE 7-10 Standard Users and Designers of Special Structures , 2011 .

[18]  Arindam Gan Chowdhury,et al.  Testing of Residential Homes under Wind Loads , 2011 .

[19]  M. Mahmood,et al.  Experiments to study turbulence and flow past a low-rise building at oblique incidence , 2011 .

[20]  Jack E. Cermak.  Progress in physical modeling for wind engineering , 1995 .

[21]  Arindam Gan Chowdhury,et al.  Hurricane Wind Power Spectra, Cospectra, and Integral Length Scales , 2008 .

[22]  Hrvoje Kozmar,et al.  Wind-tunnel simulations of the suburban ABL and comparison with international standards , 2011 .