Techno Press
Tp_Editing System.E (TES.E)
Login Search


was
 
CONTENTS
Volume 4, Number 3, June 2001
 

Abstract
At present the most popular turbulence models used for engineering solutions to flowrnproblems are the k- e and Reynolds stress models. The shortcoming of these models based on the isotropicrneddy viscosity concept and Reynolds averaging in flow fields of the type found in the field of WindrnEngineering are well documented. In view of these shortcomings this paper presents the implementationrnof a non-linear model and its evaluation for flow around a building. Tests were undertaken using thernclassical bluff body shape, a surface mounted cube, with orientations both normal and skewed at 45 o tornthe incident wind. Full-scale investigations have been undertaken at the Silsoe Research Institute with arn6 m surface mounted cube and a fetch of roughness height equal to 0.01 m. All tests were originallyrnundertaken for a number of turbulence models including the standard, RNG and MMK k- e models andrnthe differential stress model. The sensitivity of the CFD results to a number of solver parameters wasrntested. The accuracy of the turbulence model used was deduced by comparison to the full-scale predictedrnroof and wake recirculation zone lengths. Mean values of the predicted pressure coefficients were used tornfurther validate the turbulence models. Preliminary comparisons have also been made with availablernpublished experimental and large eddy simulation data. Initial investigations suggested that a suitablernturbulence model should be able to model the anisotropy of turbulent flow such as the Reynolds stressrnmodel whilst maintaining the ease of use and computational stability of the two equations models.rnTherefore development work concentrated on non-linear quadratic and cubic expansions of the Boussinesqrneddy viscosity assumption. Comparisons of these with models based on an isotropic assumption are presentedrnalong with comparisons with measured data.

Key Words
turbulence model; wind engineering; anisotropy; full-scale; bluff body; computational fluid dynamics; buildings; k- e.

Address
N.G. Wright and G.J. Easom, School of Civil Engineering, The University of Nottingham, Nottingham NG7 2RD, U.K.rnR.J. Hoxey, Environment Group, Silsoe Research Institute, Wrest Park Silsoe Bedford MK45 4HS, U.K.

Abstract
Observations of extreme wind speeds in the United Kingdom from 1970 to 1980, correctedrnfor the influence of upwind ground roughness and topography, have been analysed using the recently-developedrn

Key Words
extremes; design wind speed; exposure corrections; Method of Independent Storms.

Address
Craig A. Miller, Risk Management Solutions Ltd., 10 Eastcheap, London, EC3M 1AJ, U.K.rnNicholas J. Cook, Department of Aerospace Engineering, University of Bristol, Bristol, BS8 1TR, U.K.rnRichard H. Barnard, University of Hertfordshire, College Lane, Hatfield, Herts, AL10 9AB, U.K.

Abstract
Wind uplift rating of roofing systems is based on standardised test methods. Roof specimensrnare placed in an apparatus with specified table size (length and width) then subjected to the required windrnload cycle. Currently, there is no consensus on the table size to be used by these testing protocols in spiternof the fact that a table size plays a significant role in evaluating the performance. This paper presents arnstudy with the objective to investigate the impact of table size on the performance of roofing systems. Tornachieve this purpose, extensive numerical experiments using the finite element method have been conductedrnto investigate the performance of roofing systems subjected to wind uplift pressures. Numerical resultsrnwere compared with results obtained from experimental work to benchmark the numerical modeling. Requiredrntable size and curves for the determinations of appropriate correction factors are suggested. This has beenrncompleted for various test configurations with thermoplastic waterproofing membranes. Development ofrncorrection factors for assemblies with thermoset and modified bituminous membranes are in progress.rnGeneralization of the correction factors and its usage for wind uplift rating of roofs will be the focus of arnfuture paper.

Key Words
wind uplift; roofing system; test method; numerical model; thermoplastic; correction factor.

Address
A. Baskaran, National Research Council Canada, Ottawa, Ontario, K1A 0R6 CanadarnJ. Borujerdi, Department of Civil Engineering, University of Ottawa, Ottawa, Ontario, K1N 6N5 Canada

Abstract
The objective of this study is to understand the flow above the front edge of low-risernbuilding roofs. The greatest suction on the building is known to occur at this location as a result of thernformation of conical vortices in the separated flow zone. It is expected that the relationship between thisrnsuction and upstream flow conditions can be better understood through the analysis of the vortex flowrnmechanism. Experimental measurements were used, along with predictions from numerical simulations ofrndelta wing vortex flows, to develop a model of the pressure field within and beneath the conical vortex.rnThe model accounts for the change in vortex suction with wind angle, and includes a parameter indicatingrnthe strength of the vortex. The model can be applied to both mean and time dependent surface pressures,rnand is validated in a companion paper.

Key Words
wind; vortex; load; pressure; roof; low-rise; building; flow separation.

Address
D. Banks and R. N. Meroney, Fluid Mechanics and Wind Engineering Program, Civil Engineering Department, Colorado State University(CSU), Fort Collins, CO 80523, U.S.A.

Abstract
In the last three decades several comprehensive field measurement programs have producedrnsignificant insight into the wind effects on low-rise structures. The most notable and well published ofrnthese efforts are measurements being collected at the Wind Engineering Field Laboratory (WERFL) atrnTexas Tech University, measurements on low-rise structures in Silsoe, England and measurements onrngroups of low-rise structures collected in Aylesbury, England. Complementary to these efforts, anrnadditional full-scale field investigation program has recently collected meteorological, pressure, strain andrndisplacement data on a low-rise structure in Southern Shores, North Carolina. To date over seventy-fivernhundred data sets have been collected at the Southern Shores site in a variety meteorological conditionsrnup to and including hurricane-force winds. This paper provides details of the system, its development, andrnpreliminary assessment of its performance. A description of the field site, the instrumented structure, andrnthe instrumentation system is provided. In addition, an example of the data collected during threernhurricanes is presented. The primary goal of this paper is to provide the reader with the necessaryrntechnical details to appropriately interpret data from this experiment, which will be presented in futurernpublications currently under development.

Key Words
low-rise; full-scale; field measurements; extreme-wind; hurricanes; data collection.

Address
Michelle L. Porterfield and Nicholas P. Jones, Department of Civil Engineering, Johns Hopkins University, Baltimore, MD 21218, USA

Abstract
This paper presents an experimental study on the effectiveness of viscous-damping walls inrncontrolling the wind-induced vibrations of a building model. A simple four-story building model, squarernin plan, was constructed for wind tunnel study. In this paper the description of the model, itsrninstrumentation, and the experimental set-up and methodology are reported. The effectiveness of viscous-dampingrnwalls in reducing vibrations was investigated for different fluid levels in the walls, and at varying windrnspeeds and attack angles. The results show that viscous-damping walls are highly effective in most cases.

Key Words
viscous-damping wall; wind tunnel experiment; wind-induced vibration; vibration control.

Address
Austin D.E. Pan, Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R.rnNgai Yeung, Ove Arup & Partners Hong Kong Ltd., Level 5, Festival Walk, Tat Chee Avenue, Kowloon Tong, Hong Kong, S.A.R.


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com