"The answer is blowin' in the wind" - case study of a perforated roof screen

2021 ◽  
Vol 263 (4) ◽  
pp. 2196-2206
Author(s):  
Anthony Nash
Keyword(s):  
Wind Tunnel ◽  
Feedback Loop ◽  
Complex Tone ◽  
Angle Of Incidence ◽  
Sound Effect ◽  
Field Investigations ◽  
Perforated Sheet ◽  
Metal Panels ◽  
Physical Principles

A recently-completed building was fitted with a roof screen fabricated from perforated sheet metal panels having "U"-shaped upturned flanges. When wind impinges on the panels, complex tone clusters are generated, leading to complaints from the occupants. The unusual character of the tonal spectrum is reminiscent of a film sound effect intended to simulate a hovering extraterrestrial spacecraft. After some preliminary (but inconclusive) field investigations, it was decided to test samples of the perforated panel in a large commercial wind tunnel where the speed and angle of the airstream could be controlled. Tones generated in the tunnel were found to occur in groups or clusters - these are most pronounced when the airstream's angle of incidence is close to grazing. Gradually increasing airspeed caused the frequency of the tones to "jump" from one cluster to the next higher cluster. The physical principles of the tone-generating mechanism are not fully understood; however, it appears that structural resonances in the panel flanges are excited by air flowing over the perforate. Some form of a positive structural-acoustical feedback loop is involved since a) the frequencies within each tone cluster are quite stable and, b) damping the panel flanges extinguishes the tones.

scholarly journals Potential of dust emission resources using small wind tunnel and GIS: case study of Bakhtegan playa, Iran

2019 ◽  
Vol 9 (8) ◽  
Author(s):  
Siroos Karimzadeh ◽  
Mohammad Mehdi Taghizadeh
Keyword(s):  
Wind Tunnel ◽  
Present Model ◽  
Low Cost ◽  
Dust Emission ◽  
High Potential ◽  
Wind Speeds ◽  
Desert Areas ◽  
Medium Potential

Abstract Determination of the high potential of dust emission is a requisite affair in the management of dusts emission and as well as avoiding its risks. Wind tunnel is among the most important approaches in the study of areas having high potential in emitting dusts. Extensive dried playas and desert areas require the making of low-cost, simple, and car-portable tunnels capable of presenting comparable data of various areas even supposing not having enough precision in the model of real wind motion. In this study, we first engaged in making a car-portable tunnel with a primarily semicircle section of 38 cm height, 50 cm diameter, and 110 cm length. A fan and key appliance with the ability to change speed were used along with a simple transformer launched with car battery. Then, concentration of the pm10 dusts was measured in the various wind speeds of 1, 2.5, 4, 5.5, and 7 m/s by the help of anemometer and digital equipments. The study of Bakhtegan playa was done, as the methodology of handling with this tunnel, in 35 positions, and zoning of the results was performed via ArcGIS software. Depending on the destructibility of the shell by wind, the areas under study were categorized as low potential (34%), medium potential (37%), and high potential (29%) in emitting dusts. The results of zoning spotted the high-potential areas on the map. The usage of small tunnels, as in the present model, may be applied in order for the low-cost and fast studies of vast areas to the purpose of playas management.

scholarly journals The role of willowherbs (Epilobium) in the recovery of vegetation cover a year after use of herbicide: a case study from Central Lithuania / Ožkarožių (Epilobium) vaidmuo atsikuriant augalijai praėjus metams po herbicido panaudojimo: tyrimas centrinėje Lietuvos dalyje

2016 ◽  
Vol 22 (2) ◽  
pp. 101-112
Author(s):  
Dalytė Matulevičiūtė
Keyword(s):  
Distribution Patterns ◽  
Apple Orchard ◽  
Life Stages ◽  
Herb Layer ◽  
Field Investigations ◽  
Initial Stage ◽  
Agricultural Weeds ◽  
Very High

Abstract Several species of willowherb (Epilobium) are considered as agricultural weeds and their prevalence has become an increasing problem in agriculture. The aim of this study was to investigate the role of willowherb plants in the initial stage of vegetation succession a year after the use of glyphosate. The study was based on the examination of thirteen willowherb specimens collected in the apple orchard of 0.2 ha area in August 2008, one month after glyphosate treatment, and vegetation field investigations in the same orchard in July 2009. The coverage of herb layer, the abundance and life stages of Epilobium plants in twenty plots of 1 m2 in size were investigated. The specimens of willowherbs, which survived the glyphosate application in 2008, were identified as Epilobium ciliatum and E. tetragonum. A year after the glyphosate treatment, the willowherb plants prevailed in the vegetation. One alien (E. ciliatum) and three native (E. hirsutum, E. parviflorum and E. tetragonum) species of willowherb were found. E. ciliatum was the most abundant. This species was characterized by the highest number of reproductive and virginile plants. E. parviflorum and E. tetragonum plants were abundant with a very high proportion of reproductive plants. Only pre-reproductive plants of E. hirsutum occurred in the study plots. The reproductive plants represented more than one third of the total number of willowherb plants. The distribution patterns of willowherb species in the plots were very variable.

scholarly journals Design and Validation of a New Morphing Camber System by Testing in the Price—Païdoussis Subsonic Wind Tunnel

Aerospace ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 23 ◽  
Author(s):  
David Communier ◽  
Ruxandra Mihaela Botez ◽  
Tony Wong
Keyword(s):  
Wind Tunnel ◽  
Unmanned Aerial Vehicle ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Trailing Edge ◽  
Subsonic Wind Tunnel ◽  
Aerial Vehicle ◽  
Stall Angle

This paper presents the design and wind tunnel testing of a morphing camber system and an estimation of performances on an unmanned aerial vehicle. The morphing camber system is a combination of two subsystems: the morphing trailing edge and the morphing leading edge. Results of the present study show that the aerodynamics effects of the two subsystems are combined, without interfering with each other on the wing. The morphing camber system acts only on the lift coefficient at a 0° angle of attack when morphing the trailing edge, and only on the stall angle when morphing the leading edge. The behavior of the aerodynamics performances from the MTE and the MLE should allow individual control of the morphing camber trailing and leading edges. The estimation of the performances of the morphing camber on an unmanned aerial vehicle indicates that the morphing of the camber allows a drag reduction. This result is due to the smaller angle of attack needed for an unmanned aerial vehicle equipped with the morphing camber system than an unmanned aerial vehicle equipped with classical aileron. In the case study, the morphing camber system was found to allow a reduction of the drag when the lift coefficient was higher than 0.48.

scholarly journals A wind-tunnel case study: Increasing road cycling velocity by adopting an aerodynamically improved sprint position

2019 ◽  
pp. 175433711986696
Author(s):  
Timothy Crouch ◽  
Paolo Menaspà ◽  
Nathan Barry ◽  
Nicholas Brown ◽  
Mark C Thompson ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Time Trial ◽  
Force Measurements ◽  
Sampling Errors ◽  
Repeated Testing ◽  
Road Cycling ◽  
Wind Tunnel Study

The main aim of this study was to evaluate the potential to reduce the aerodynamic drag by studying road sprint cyclists’ positions. A male and a female professional road cyclist participated in this wind-tunnel study. Aerodynamic drag measurements are presented for a total of five out-of-seat sprinting positions for each of the athletes under representative competition conditions. The largest reduction in aerodynamic drag measured for each athlete relative to their standard sprinting positions varied between 17% and 27%. The majority of this reduction in aerodynamic drag could be accounted for by changes in the athlete’s projected frontal area. The largest variation in repeat drag coefficient area measurements of out-of-seat sprint positions was 5%, significantly higher than the typical <0.5% observed for repeated testing of time-trial cycling positions. The majority of variation in repeated drag coefficient area measurements was attributed to reproducibility of position and sampling errors associated with time-averaged force measurements of large fluctuating forces.

scholarly journals EXPERIMENTAL, NUMERICAL AND ANALYTICAL INVESTIGATIONS OF WIND-INDUCED NET PRESSURES FOR INDUSTRIAL BUILDINGS WITH ENVELOPE POROSITIES

2016 ◽  
Vol 7 ◽  
pp. 58
Author(s):  
Vanessa Saubke ◽  
Rüdiger Höffer
Keyword(s):  
Spatial Distribution ◽  
Numerical Model ◽  
Wind Tunnel ◽  
External Pressure ◽  
Navier Stokes ◽  
Industrial Building ◽  
Wind Tunnel Experiments ◽  
Industrial Buildings ◽  
External Pressures

The magnitude and the spatial distribution of wind-induced net pressures (external and internal) on buildings are frequently discussed among research communities and construction industries. This paper deals with this topic based on a case study about an industrial building in Denmark, which was damaged due to the wind impact during a storm when a large part of the roof covering was blown off. In order to detect the reason for the damage the wind-induced loads were studied by i) wind tunnel experiments on the external pressures due to different wind directions, ii) analytical investigations of internal pressure due to envelope porosities and planned openings and iii) numerical analyses for the internal and the external pressure. The Reynolds averaged Navier-Stokes (RANS) method is employed to build a numerical model. The experimental, analytical and numerical results are compared with the indicated characteristic loads from the Eurocode.

scholarly journals Institutional Dynamics in International Organizations: Lessons from the Recruitment Procedures of the European External Action Service

2014 ◽  
Vol 35 (12) ◽  
pp. 1793-1811 ◽  
Author(s):  
Zuzana Murdoch ◽  
Benny Geys
Keyword(s):  
Organizational Change ◽  
International Organizations ◽  
Feedback Loop ◽  
Focal Point ◽  
External Action ◽  
Theoretical Framework ◽  
Theoretical Argument ◽  
Institutional Dynamics ◽  
Formal Procedures

This article examines how organizational designs develop by proposing a novel theoretical framework that views organizational change as resulting from a dialectic process between interpretive agents. The key claim is that existing formal procedures (such as recruitment processes, our empirical focal point) are subject to involved actors’ interpretive efforts. This results in a bargaining situation based on the interpretations of the principal actors, which may induce a feedback loop whereby the original procedures are amended. The empirical relevance of the theoretical argument is illustrated via a case study of the hiring procedures in the European External Action Service.

Human Factors Influencing Wind Tunnel Productivity — A Case Study

1985 ◽  
Vol 29 (11) ◽  
pp. 1046-1050
Author(s):  
Denise C. R. Benel ◽  
Margery Davidson Boulette ◽  
Larry W. Avery
Keyword(s):  
Wind Tunnel ◽  
Human Factors ◽  
Factors Influencing

Key Point of Bridge Damage Caused by Glacial Debris Flows along International Karakorum Highway, Pakistan

2012 ◽  
Vol 256-259 ◽  
pp. 2713-2723 ◽  
Author(s):  
Li Ping Liao ◽  
Ying Yan Zhu ◽  
D.H.Steve Zou ◽  
Zhi Quan Yang ◽  
Waseem Muhammad ◽  
...  
Keyword(s):  
Debris Flows ◽  
Northern Pakistan ◽  
Detailed Data ◽  
Prevention Measures ◽  
Improvement Project ◽  
Field Investigations ◽  
Abrasive Erosion ◽  
Bridge Damage ◽  
The Impact

Glacial debris flows along International Karakorum Highway (KKH) connecting northern Pakistan with China, are always causing so extreme threats to a majority of bridges built along KKH. So the improvement project of KKH has been being carried out by China Road & Bridge Corporation in 2008. However it is necessary to collect the detailed data about the damages to bridges and obtain the most dangerous key position. The series of field investigations from 2008 to 2011 demonstrate that the damages are classified into four categories: deposition under bridge, abrasive erosion, impact on piers or abutment and collapse due to buoyancy. Statistics indicate deposition under bridge is the most dominant damage whereas the most serious damage is the impact on piers or abutments. Therefore a case study on key point is made for the typical bridge subjected to impact from Ghulkin glacial debris flow. Finally prevention measures are given.

Design effectiveness of wind tunnel studies for buildings of intermediate height

1977 ◽  
Vol 4 (1) ◽  
pp. 96-116 ◽  
Author(s):  
David Surry ◽  
Robert B. Kitchen ◽  
Alan G. Davenport
Keyword(s):  
Wind Tunnel ◽  
Building Codes ◽  
Comprehensive Model ◽  
Wind Action ◽  
Model Study ◽  
Design Effectiveness ◽  
Wind Tunnel Study

The components of a comprehensive model study involving both meteorological and wind tunnel investigations are discussed. An application of the procedures is illustrated by a case study involving a building of intermediate height and unusual geometry. The effectiveness of the wind tunnel study is presented in terms of comparisons of the resulting predicted loads with those derived from building codes, and in terms of the improved knowledge of wind action available to the designer.

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