# Journal of Wind Engineering and Industrial Aerodynamics

Published by Elsevier

Online ISSN: 0167-6105

Published by Elsevier

Online ISSN: 0167-6105

Publications

Article

This paper is an attempt to provide additional insight into the limitations of the current tornado data by viewing the problems across the longest possible time period. It is suggested here that the position of the various maxima and minima of wind speed probability are not known with accuracy because of inherent population bias in both tornado documentation and the Fujita scale rating process. The author defines the periods of tornado documentation, assesses the consistency of F-scale ratings for F2–F5 (referred to as “significant”), broadens the standards for F-scale application, and applies those standards through three of the five data base periods. 1880–1915 tornado outbreaks are compared to more recent distribution maps. Population bias is suggested as a controlling factor in the distribution pattern of Kansas tornadoes. An adjustment for population shifts the Wichita maxima to the west by 100 miles and turns the Kansas City maxima into a relative minima. A subregional minima is noted for Tarrant Country (Fort Worth), Texas.

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Article

Measurements of wind pressures on a one-tenth scale model of the Texas Tech Building in a large wind tunnel are described. The mean and RMS pressure coefficients obtained from the model for critical corner tappings for oblique wind directions, are in excellent agreement with the corresponding full-scale values. The largest minimum pressure coefficients for these tappings are approximately 20% less in magnitude than the corresponding full-scale values. The increased Reynolds number for the present test series is believed to play a significant part in the greatly improved agreement obtained.

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Article

The Ahmed body is a simplified car used in automotive industry to investigate the influence of the flow structure on the drag. Wake flow is two-dimensional for low incidences of the rear slant, then becomes three-dimensional when the angle of the hatchback approaches 30° and reverts to two-dimensional behavior for angles higher than 30° where above this angle, a sudden drop in drag occurred. In this paper, we investigate numerically the flow around the Ahmed body for the base slant angles 25° and 35°. Results are compared with experimental data. The two-dimensional behavior of the flow, for the slant angle 35∘, is well predicted, whereas the transition of the wake to a fully three-dimensional, for the slant angle 25°, is not reproduced. Therefore, the flow around the Ahmed body with 25° slant angle can be considered an open challenge for turbulence modeling.

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Article

Long span suspension bridges are flexible structures which are highly sensitive to the action of the wind, hence aerodynamic performance often becomes a governing factor in the design process. The magnitude of the East Bridge, a 3 span suspension bridge of span lengths 535, 1624 and 535 m, has warranted an aerodynamic design process which involves state-of-the-art model testing and analytical procedures. The present paper focuses on the use of wind tunnel test results in the design of the East Bridge. Particular attention is given to the strategy adopted for wind tunnel testing, and to selected results obtained. Considerations for the bridge in service cover aerodynamic stability, dynamic wind loads and vortex shedding response of the girder. For the erection phase aerodynamic stability of the girder is treated in some detail.

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Article

A brief review is undertaken of the general effects of strong winds on British Rail (BR) operations. Focusing, in particular, on railway vehicle overturning the effect of the great storm of 1987 on BR operations in the South-east is examined from BR contemporary sources. These show in graphic detail the degree of destruction and the gradual paralysis of the network as it occurred early on 16th October. A discussion is undertaken of the reasons for the absence of a vehicle overturning incident despite it being likely that wind strengths were sufficient for this to happen. It is concluded that this was due to the time of day of the storm peak and the rail system becoming fail-safe by tree fall.

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Article

This paper presents flutter analysis of a super-long span (central span 1020 m) cable-stayed bridge based on experimentally extracted 18 flutter derivatives. In the analysis, the aeroelastic forces to be used in the equation of motion utilize rational function approximation of flutter derivatives. The equation of motion is finally recast into aeroelastically modified modal state space form, which yields an unsymmetric eigenvalue problem. The complex eigenvalues thus obtained are used to identify the critical flutter condition. The numerical analysis is performed on a three-dimensional (3D) finite element model of the bridge. The results show that critical flutter velocity based on theoretical flutter derivatives is exceptionally higher than that based on experimental flutter derivatives.

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Article

A 183 m reinforced concrete chimney for a coal-fired power station was instrumented in the latter part of its life during the construction of a replacement chimney. Because of concerns about large-amplitude response induced by interference effects from the new chimney in the prevailing upwind direction, a response monitoring system was installed, quickly followed by a tuned mass damper (TMD) system. As well as providing live display of the chimney response, the monitoring system was also used to check the functioning of the TMD. The monitoring system featured a direct implementation of the stochastic subspace identification procedure in the ‘virtual instrument’ controlling the system, so that modal damping values for the system were displayed automatically, in real-time. The system thus provided an immediate visual indication of increased damping levels during strong winds, showing the correct functioning of the TMD. The paper describes the chimney, the monitoring system and its installation, the data processing and system identification procedure, together with performance data before, during and after installation of the TMD.

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Article

When stochastic simulation of inflow turbulence random fields is employed in the analysis or design of wind turbines in normal operating states, it is common to use well-established standard spectral models represented in terms of parameters that are usually treated as fixed or deterministic values. Studies have suggested, though, that many of these spectral parameters can exhibit some degree of variability. It is not unreasonable to expect, then, that derived flow fields based on simulation with such spectral models can be in turn highly variable for different realizations. Turbine load and performance variability would also be expected to result if response simulations are carried out with these variable flow fields. The aim here is to assess the extent of variability in derived inflow turbulence fields that arises from the noted variability in spectral model parameters. Simulation of these parameters as random variables forms the basis of this study. A commercial-sized 1.5 MW concept wind turbine is considered in the numerical studies. Variability in turbulence power spectra at field points on the rotor plane and in turbulence coherence functions for separations on the order of a rotor diameter and smaller is studied. Using time domain simulations, variability in various wind turbine response measures is also studied where the focus is on statistics such as response root-mean-square and 10-min extreme estimates. It is seen that while variability in inflow turbulence spectra can be great, the variability in turbine loads is generally considerably lower. One exception is for turbine yaw loads whose larger variability arises due to sensitivity to a coherence decay parameter that is itself highly variable. Finally, because reduced-order representations of turbulence random fields using empirical orthogonal decomposition techniques allow useful physical insights into spatial patterns of flow, variability in the energy distribution and the shapes of such empirical eigenmodes is studied and a simplified model is proposed that retains key variability sources in a limited number of modes and that accurately preserves overall inflow turbulence field uncertainty.

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Article

Wind Ship commenced intensive research on wind propulsion for ships in early 1979. The Company's 1981 comprehensive research report to the U.S. Maritime Administration entitled “Wind Propulsion for Ships of the American Merchant Marine” identified the rigs with best potential for early commercial development and developeda conceptual design for a 20, 000 DWT motor ship with auxiliary wing sails. Wind Ship has now developed and tested at sea a 3, 000 ft2 soft sail cat rig and also designed a 3, 000 ft2 Wing Sail based on the principal of feathering (without flutter) as a means of reefing or furling. The wing sail's flutter inception, gust response and operating gear have been tested on a 300 ft2 model using a fully instrumented test stand. Wind Ship has also extensively tested a 90 ft2 Magnus Effect rotor at sea. The results of these testing programs and the conclusions reached are discussed, along with Wind Ship's performance, economic and aeroelastic models.The merits of other high lift rigs such as the Walker Wing Sail and Cousteau TURBOSAIL are discussed. The need for accurately predicting performance at sea and economics of various rig alternatives is discussed. Wind Ship's approach to such analyses is described. A summary results from the analyses of a variety of commercial vessels and oceanographic vessels including SWATH type ships is presented. Overall economic, market, environmental and political factors are discussed.

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Article

Previous studies of wind-related accidents have concentrated on the effects of individual high wind storms on road accidents. This study examines the wind hazard and its effects on accident occurrence. Police road accident data were analysed for the period 1980–1990. Wind-related accidents were found to be only a small percentage of total overall accidents recorded by the police. Despite accounting for so few accidents, the author felt it was important to consider the effects of high winds on accident severity. In order to demonstrate this severity ratios were used in the analysis. However, no relationship could be established. To examine exposure to risk weather data were included in the analysis. The proportion of time high winds were recorded over a given time period was compared to the percentage of total accidents occurring in high winds over that same period. If high winds did not effect the likelihood of an accident occurring then the proportion of accidents occurring in high wind would equal the proportion of time for which high winds were recorded. In fact, the proportion of accidents occuring in high winds was almost double the percentage duration of high winds.

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Article

The Humber Bridge was the subject of an extensive monitoring campaign during 1990 and 1991 during which a large body of experimental data describing the loading and response processes was obtained. Some 70 instruments were used to measure wind speed and direction together with displacement, acceleration, rotation and temperature of the structure. The aim of the exercise was to validate mathematical modelling of the response of long span bridges to wind and to provide a picture of the relationships between the loading and response parameters. A full description of the instrumentation and monitoring arrangements is given together with some example results.

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Article

The wind load requirements of the Uniform Building Code™ (U.B.C.), was promulgated by the International Conference of Building Officials (ICBO), have historically been based on the American National Standards Institute (ANSI) standard A58.1, currently the American Society of Civil Engineers (ASCE) standard ANSI/ASCE 7–88. The provisions contained in the 1991 edition of the U.B.C. remain based on ANSI A58.1-1972 with updating to ANSI A58.1-1982 and other changes.Additions and refinements have been made to the 1991 U.B.C. to bring the wind load design provisions of Chapter 23 into closer agreement with ANSI/ASCE 7–88, while retaining the code's traditional simplified approach. For the first time, an exposure similar to Exposure D in the standard has been added for coastal areas and shorelines, along with appropriate new coefficients to govern the design of buildings sited adjacent to large bodies of water.Also new to the 1991 U.B.C. are detailed, prescriptive criteria for conventional wood and masonry buildings located in high-wind areas. These criteria modify existing provisions in Chapters 24 and 25 for construction of such buildings without an engineered design. The criteria were developed over a three-year period to provide conventional buildings with improved wind resistance and to mitigate damage from hurricanes, tornadoes and other high-wind events.

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Article

The Hardanger Bridge is currently under construction in Norway. It will have a main span of 1310 m and a girder that is only 18.3 m wide, which implies that wind-induced vibration is a major concern in the design. Buffeting response and flutter analysis of the Hardanger Bridge are treated in this paper. The self-excited forces are modelled using aerodynamic derivatives obtained from free vibration tests, quasi-steady theory, and a suggested modified quasi-steady theory. The stability limit predicted using aerodynamic derivatives corresponded well with the wind tunnel results, while the quasi-steady theory severely underestimated the critical mean wind velocity for the section model used in the wind tunnel tests. A new set of modified quasi-steady coefficients are suggested, where the experimental results of the aerodynamic derivatives are used to obtain frequency-independent model coefficients. The critical velocities predicted by the modified quasi-steady coefficients differ only by 4–5% from estimates based on the aerodynamic derivatives. The response predicted by the suggested simplified aerodynamic model is also presented, and the results indicate that adequate estimates are achieved.

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Article

Recently, in Japan, a growing interest has arisen in the development and securing of the amenities required for living spaces. The reduction of the uncomfortable sway motion of high-rise buildings, induced by comparatively strong winds, is a subject of central importance in this area.The authors have been able to develop a motion reduction device equipped with new mechanism. This device is actually a tuned active damper (TAD), which is equipped with both a tuned spring system and a control system. It is able to act in dual directions. The tuned spring system has a multi-stepped pendulum with a period of 6.0 sec. and an AC servomotor is used for the control system. Two devices of this type are installed on the first floor of the penthouse of the MM 21 Landmark Tower.The height of the tower is 296m and the location of the installation of the devices is at 282m. The devices are small and have an effective weight ratio of 0.6%. The criterion for habitability has been fixed at 5.8 cm/sec2 (rms value) for the response acceleration at the top of the building in light of the ISO 6897. This criterion is set up for a wind force with a return period of five years. The installation of the tuned active dampers can reduce the building's degree of swaying motion by more than , which effectively satisfies the criterion.These devices were designed with thorough consideration given to safety. This has indeed been confirmed through the use of a test employing a scale model.

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Article

The aerodynamics of a Sparkman and Stephens 24-foot sailing yacht was investigated. Full-scale pressure measurements were performed on the mainsail and the genoa in upwind condition. Pressure taps were adopted to measure the pressures on three horizontal sections on the windward and leeward sides of the two sails. Several trims and apparent wind angles were tested. The present paper shows the pressure distributions on the sails and correlates the measured pressures with the flow pattern. In particular, leading-edge laminar separation bubble, turbulent reattachment and turbulent separation are discussed. Pressure measurements are also adopted to draw some trim guidelines.

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Article

Full-scale investigation of the mean and oscillating pressure flow field around a 240-m chimneyMeasurements of the mean and oscillating pressure at three levels of a 240-m concrete tapered chimney are described.Wind velocity, upstream and on the front part of the chimney, and vibration of the structure at the top were also measured. All the data were digitalized and recorded continuously.Mean pressure distribution, correlations and spectra were evaluated at three levels which allow to understand the longitudinal evolution of the vortex shedding and its characteristics at fixed level.RésuméL'écoulement autour d'une cheminée tronconique de 240 m de hauteur, est étudié à partir de mesures de pression moyenne et fluctuante sur trois couronnes.Outre la distribution des valeurs moyennes et des écarts-type de pression sur plusieurs couronnes, on s'est particulièrement intéressé à la détermination des caractéristiques de la structure tourbillonnaire sur une couronne et à son évolution en hauteur.

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Article

This paper describes experiments with an aeroelastic model of a suspended footbridge. Its sensitivity to the effect of vortex separation at wind velocities from 15 to 17.5 ms−1 was ascertained. Instability of the flutter type was not observed. To reduce the amplitude of flexural vibrations dampers were designed to be installed in the railing posts.

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Article

Numerical predictions are presented for flow through and in a model forest on a two-dimensional hill. Calculations are performed with a finite volume numerical algorithm, using non-staggered non-orthogonal grid systems. To eliminate false diffusion errors, the convective terms in the governing equations are discretized using a highly accurate numerical scheme constructed from the class of total variation diminishing (TVD) schemes. The time averaged Navier-Stokes equations are closed by an extended k-ϵ eddy viscosity model including terms due to the drag caused by the canopy. The predictions are compared with reported LDV measurements obtained in an atmospheric boundary layer wind tunnel for different forested hill geometrical configurations. The calculations show good agreement with measurements concerning the strong influence of the tree cover on the separated flow region.

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Article

The need to confirm the analytical solutions for the mean wind velocities over simple two dimensional hill shapes is a basic first step in the development of a practical prediction technique suitable for more complex terrain. For this purpose, a wide range of experimental data from full scale, model and numerical studies are collated and presented in the form suggested by current theory. It is shown that when the velocity data for a certain height above the crest is presented as a non-dimensional incremental-velocity which only depends on the overall hill shape, the data behave in a coherent fashion that is adequately predictable.

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Article

This paper presents and discusses the results of wind tunnel measurements of the pressure distributions on the lateral sides of a 2D square prism with vibrating leading edge flaps. The flaps were driven with sinusoidal motion at different frequencies and amplitudes. Differential pressures across the lateral sides of the model were sampled simultaneously to give sets of signals at five different distances from the front surface. RMS lift coefficients and lift spectra were calculated by integrating pressures. It was found that increasing the flapping frequency and amplitude decreased the RMS lift coefficient up to 70%. An optimum mean flap angle existed with specific frequency and amplitude. Frequency domain analysis revealed that increased flapping amplitude disrupted vortex shedding, while increased flapping frequency suppressed pressure fluctuations in a wide frequency band. Co-spectra results showed that the flapping action affected the pressure on the side of the model as if the onset flow was made more turbulent. The results suggest that the vibrating flaps introduce a force fluctuation at the flap operating frequency. It appears as if the fluctuating velocity components introduced by the flapping motion work in a manner similar to small-scale turbulence in turbulent onset flow and change the characteristics of the shear layer. Preliminary tests using one flap gave results which confirmed the presence of completely different flows on the opposing faces.

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Article

In big cities, vehicle exhaust gases can be trapped inside deep and poorly ventilated urban complex geometries (street-canyons, tunnels and covered roadways). The covered roadway is a typical configuration characterized by high emissions, poor ventilation and exposure to large numbers of people. High concentration of pollutant gases may be expected with low winds, or when the wind is oriented perpendicular to the covered roadway axis. To understand the wind effects on the transport and dispersion processes close to a covered roadway, we have conducted a numerical modeling study using the 2D Large Eddy Simulation approach. The Navier–Stokes equations are integrated by a finite volume method and then solved in time using the projection method, allowing for decoupling pressure from velocity. For the turbulence, a dynamic mixed subgrid scale model is introduced to take into account the unresolved small-scale effects. The covered section is open to one side; two aspect ratios (width to height) for the covered section are tested: 3.6 and 7.2. Two wind direction cases are studied. Our results, compared with the wind-tunnel experiment of Dabberdt et al. Int. J. Vehicule Design, 20(1–4) (1998) 96, show good agreement. The numerical simulations give detailed information on pollutant transport mechanism within the covered section. The dispersion process is highly dependent on the flow turbulence and is influenced by both the geometry of covered section and the wind direction. When the open end of the covered section is to windward, a dominant anticyclonic vortex occupies the entrance of the covered section. The dispersion process is advection dominated due to the fact that the pollutant is carried outside the covered region by large unsteady structures produced in the shear region. When the open section is to leeward, the transient solutions confirm that the gas dispersion from the covered section takes place through an intermittent “vortex and purging” release, governed by the interactions between the large structures in the vicinity of the open side.

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Article

Recent research in fluid mechanics has indicated that the non-universality of growth rate parameters in bluff body wakes might be related to the base wake vortex dynamics. This aspect relates to possible aerodynamic control strategies for wind engineering applications.Herein a passive slot control technique is numerically (LES) investigated. It is shown that the slot flow penetrates in the near-wake region generating a Kelvin–Helmholtz-type instability that mitigates the vortex shedding formation. A more elongated wake bubble associates to drag reduction and the decrease in lateral pressure fluctuations reduces the fluctuating lift coefficient.

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Article

This paper is concerned with the question of an appropriate turbulence model for the computational modelling of bridge deck aero-elasticity. A detailed examination of the suitability of different turbulence models for simulating various aero-elastic phenomena leads to the conclusion that the two equation k–ω RANS turbulence model strikes the right balance between computational efficiency and accuracy in simulating the flow regime. In order to test this hypothesis a rectangular prism with B/D=4 is taken as an example structure and the flutter derivatives are identified from FSI simulations for both low and medium turbulent flow regimes. The simulations are carried out using a block iterative sequential coupling routine that allows for the exploitation of existing fluid and structural solvers. The results show that the k–ω can adequately model the motion induced shear layer dynamics that are necessary for simulating FSI. The results also demonstrate the potential benefits of computational FSI studies in that flutter derivatives (and other aerodynamic coefficients) can readily be obtained without some of the problems encountered in wind tunnel tests.

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Article

A numerical simulation has been performed of the disturbed flow through and over a two-dimensional array of rectangular buildings immersed in a neutrally stratified deep rough-walled turbulent boundary-layer flow. The model used for the simulation was the steady-state Reynolds-averaged Navier–Stokes equations with linear and non-linear eddy viscosity formulations for the Reynolds stresses. The eddy viscosity was determined using a high-Reynolds number form of the k–ε turbulence-closure model with the boundary conditions at the wall obtained with a standard wall-function approach. The resulting system of partial differential equations was solved using the SIMPLE algorithm in conjunction with a non-orthogonal, colocated, cell-centered, finite volume procedure. The predictive capabilities of the high-resolution computational fluid dynamics (CFD) simulations of urban flow are validated against a very detailed and comprehensive wind tunnel data set. Vertical profiles of the mean streamwise velocity and the turbulence kinetic energy are presented and compared to those measured in the wind tunnel simulation.

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Article

Experiments on rectangular prisms with fineness ratio (width-to-depth ratio) of 2, 3 and 4 are reported in this paper. The tests were performed in the 2D test section of a pressurised wind tunnel in smooth and turbulent flow for Reynolds numbers ranging from 0.15×106 to 4×106, for Mach numbers not exceeding 0.30. Steady and unsteady measurements of surface pressures on a chord-wise strip as well as overall lift, drag and pitching moment on the model were carried out. Flow fluctuations in the wake were also captured with a hot-film probe. The experiments helped define the influences of Reynolds number, after-body length, angle of wind incidence and approaching flow turbulence on the aerodynamics of rectangular prisms. The influence of the edge treatment of the rectangular prisms, i.e. square edges versus small or large chamfer, was also studied at high Reynolds numbers. The paper presents a detailed description of the experiments and an overview of the effects of Reynolds number, Mach number and flow turbulence observed in the study.

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Article

Aerodynamic buffeting is experimentally investigated for moderate Reynolds number, turbulent flows around two- and three-dimensional bluff bodies in tandem. Combining flow visualizations, surface pressure and velocity measurements, changes in aerodynamic loading and macroscale flow features are related. For large obstacle separations, it is found that when surface-mounted prisms are placed in thin boundary layers, loading and wake dynamics are similar to those found for cylinders suspended in free streams. However, important differences are identified for smaller gaps, which can be generally attributed to greater streamline curvature for three-dimensional configurations.

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Article

Various comparisons between the observed across-wind response of a 300m concrete chimney and the response predicted by the well known model developed by Vickery and Basu [1983] are presented. It is shown that the model performs remarkably well when the predicted response is based on the observed total damping, which suggests that the aerodynamic damping is positive for the small amplitudes characteristic of concrete chimneys.

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Article

A sail-assisted version of a 33-foot fishing vessel, the Peter Norlin-designed New Deal 33, has been tested by Nordland Research Institute. Speed and fuel consumption for different combinations of sail and engine power have been measured under various wind situations and loading conditions.Having a low-resistance hull and a highly efficient propeller plant, the vessel even without sail assistance showed an outstanding performance as regards fuel economy, compared to other modern Norwegian fishing vessels of similar size, speed and capacity. The fuel consumption values were less than 50% of the corresponding figures for comparative vessels. By means of sail assistance this low fuel consumption could be reduced by approximately 10–15% in winds of 10 to 20 knots.In order to justify investing in a sailing rig and the bother of operating it on such a fuel efficient vessel as this, the rig has to be both effective, inexpensive and of as little inconvenience to the fishing and manoeuvring operations as possible. The sail plan on the vessel tested consisted of a large furling genoa and a small gaff mizzen. In order to improve the economy of the sail assistance, a cheaper sailing rig is suggested.

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Article

A large eddy simulation (LES) is performed for the turbulent flow around a circular cylinder at ReD=3900 with a cell-centered finite volume code that solves the compressible Navier–Stokes equations. The results are compared with the direct numerical simulation of Ma et al. (J. Fluid Mech. 410 (2000) 29) and the experiments of Ong and Wallace (Exp. Fluids 20 (1996) 441). It is shown that short averaging times, which have been used by several previous LES do not lead to converged mean values. For the largest averaging time used in this study, the results are in good agreement with the aforementioned data. In addition, the realizability of the modeled subgrid scale stresses and the computed Reynolds stresses is analyzed.

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Article

The engineering interest about dune fields is dictated by the their
interaction with a number of human infrastructures in arid environments. The
aerodynamic behaviour of sand dunes in atmospheric boundary layer belongs to
the class of bluff bodies. Because of their simple geometry and their frequent
occurrence in desert area, transverse sand dunes are usually adopted in
literature as a benchmark to investigate dune aerodynamics by means of both
computational or experimental approach, usually in nominally 2D setups. The
writers suspect the flow in the wake is characterised by 3D features and
affected by wind tunnel setup - e.g. blockage effect, duct side wall boundary
layer, incoming velocity profile - when experimental studies are carried out.
The present study aims at evaluating the 3D flow features of an idealised
transverse dune under different setup conditions by means of computational
simulations and to compare the obtained results with experimental measurements.

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Article

This paper focuses on a general quasi-steady approach for evaluation of three-dimensional (3D) galloping stability and buffeting response of elastic structures such as bridges and towers. The buffeting response is obtained as a time history, solving the generalised state equation of dynamic equilibrium. Its homogeneous solution allows evaluation of the galloping stability (linear formulation). The time histories of the wind velocities required for the buffeting analysis are numerically generated. Buffeting responses of the Millennium Footbridge over the Thames River in London, are simulated and the statistics of the results are compared with a conventional frequency domain method. Stability and accuracy of the integration are examined to establish the range of the solution parameters. The galloping stability analysis is verified on the I235 Pedestrian Bridge, Des Moines, Iowa, where the results are compared with the wind tunnel predictions.

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Article

A comprehensive wind tunnel test program was conducted to investigate interference excitation mechanisms on translational and torsional responses of an identical pair of tall buildings. Motion responses of a three-degree-of-freedom aeroelastic building model were measured. Both upstream and downstream interference effects were studied in this research. The experimental results showed that with an open terrain wind model, both dynamic translational and dynamic torsional responses generally increased under interference effects for an operating reduced wind velocity of 6. Measured response spectra indicated that amplified along-wind, cross-wind and torsional responses were largely induced by the wake of an upstream interfering building. The significance of interference effects and the dominant interference mechanisms depended upon the location of the aeroelastic model in the wake region. Furthermore, coupled translational–torsional motion of the aeroelastic building model tested was found to cause only small increases in the resultant motions at the building corner.

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Article

The present paper deals with the actions and effects of wind on the Park Tower of Milan, a 100 m high steel tower built in 1933 on the occasion of the Fifth Triennal Exhibition of Decorative Arts. It provides a critical comparative picture of the assumptions and forcasts made by the designers of that epoch, the estimates furnished by present national standards and advanced dynamic analyses, the first results of full-scale experiments.

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Article

Accuracy of gust simulation by fitting an autoregressive moving averaging model for the u and w components of Kàrmàn's turbulent structure is discussed. The autoregressive process is directly estimated using the theoretical autocorrelation function of the turbulent structure. The power spectra and the scales of turbulence of the autoregressive moving averaging model are compared with the theoretical values of the turbulent structure. The gust components of the Kàrmàn's turbulent structure are able to be simulated using the autoregressive moving averaging model with satisfactory accuracy.

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Article

The authors (J. Wind Eng. Ind. Aerodynam. 89 (2001) 341) presented a time domain framework for predicting the buffeting response of slender structures utilizing aerodynamic forces based on the quasi-steady theory. The example studied clearly demonstrated the significant influence of structural nonlinearities on the buffeting response, and reaffirmed the overall versatility of the time domain analysis approach. In the light of the time domain presentation in this paper, we would like to offer some comments which we believe would expand the scope of the time domain approach as applied to bridge buffeting response. Our discussion focuses on three key aspects: the simulation of the random wind field, the quasi-steady aerodynamic force model and the element discretization as presented in this paper.

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Article

The present paper describes an evaluation of turbulent wind data acquired at the measuring tower installed in the Solling spruce forest by the Institute of Bioclimatology at the Georg Augustus University at Goettingen. Simultaneous wind velocity data were analysed from two measuring points: at the mixing layer above the forest canopy, and at a height of 2 m, well within the forest, by means of quadrant analysis, correlation analysis and wavelet techniques.The results suggest two types of phenomena coexisting in the upper mixing layer region of the flow: large-scale oscillations independent of the roughness type, and smaller-scale structures, of frequent penetration, related to vertical transport phenomena.The aim of the present work was to describe aspects of the mechanism involved in the generation of the known canopy size vortices, which transport momentum from the mixing layer region deep within the canopy. This work discusses aspects of the interaction between the mixing layer region above the forest and a particular low mean velocity region near the ground, submitted to intermittent shear by the nearby vortex structures and influenced by features of the canopy top mixing layer.

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Article

Obstacles like buildings on the ground surface affect the flow in the lower part of the atmosphere. Wind tunnel measurements of the wind velocity field and, more qualitatively, the turbulence intensities have been made for both idealized and realistic building patterns and approach flow directions. The relationship between the building pattern and the height to which the disturbances extend is significant. For a smooth uniform pattern, it is about the same as the height of the buildings; for inhomogeneous rough terrain, the disturbances extend to about twice the building height. As the roughness changes, the growth of the developing internal boundary layer was observed and compared with results from the literature. The agreement is fairly good.

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Article

Due to the radical strides of computers and networks, computational science and engineering (CSE) such as CFD have been in the path of progress by technical innovation. This progress has expanded the possibility of applying CSE to practical subjects. However, following the change, application software has become large and complicated. Thus, the key for further improvement of CSE including CFD is the way in which practical engineering software (PES) will be developed. In this paper we discuss the development strategy of PES, and describe a virtual experiment system and a steering system which are important basic technologies for the next generation PES.

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Article

This paper proposes a random decrement (RD) based method to identify the modal parameters of a linear dynamic system, when only forced acceleration responses are available for use. The RD based method evaluates response data in the time and, then, frequency domains by correlating the RD technique with fast Fourier transform based algorithms and a linear least square procedure. However, the effect of the RD signatures of input forces that is added in the RD signatures of the acceleration responses must be addressed. In response to this need, a novel frequency response function (FRF) approach for the acceleration responses, with a modification of the traditional one, is verified as a first step. Subsequently, the derivation of the RD based method follows the concept of the FRF approach to achieve the theoretical basis of the FRF defined for the RD signatures. Numerical simulations of a 2DOF linear dynamic system loaded by white noise forces and simulated wind forces foster applicability of the RD based method. Applications of the Ibrahim time domain algorithm and the vector RD technique to the forced acceleration responses are also discussed.

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Article

A simple empirical formula for the estimation of across-wind and torsional acceleration of prismatic high rise buildings is examined through a wind tunnel test. In the wind tunnel test, the side ratios (D/B, D:depth, B:breath) of the models are between 0.3 and 5, and the aspect ratio H/√A H:building's height, A:plan area) are between 4 and 8. As to the approaching flows, two kind of boundary layers representing open and urban flow conditions are applied. In the formula the response acceleration is expressed in proportion to the power of the mean wind velocity. The characteristics values derived from the formula are compared with the values from the test, the codes and other studies. Furthermore an expression for the power spectral density of the across-wind overturning moment is suggested for better estimation of the across-wind acceleration. There is a difference of less than 10% between the estimated value obtained through the use of the proposed equation and the value from the wind tunnel test.

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Article

This paper examines the ability of two semi-empirical approaches to estimate wind induced accelerations in tall buildings as compared to results obtained from wind tunnel measurements on scale models. The estimating methods include a code based approach found in The National Building Code of Canada (NBCC) and an alternate semi-empirical approach which incorporates more detailed building and wind properties in the analysis steps. These techniques are applied to 48 buildings tested to date.

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Article

This paper describes the results of full-scale measurements of wind pressure and wind-induced response acceleration for an 18 storey building 68 m high. It also gives estimates of the response acceleration of this building in accordance with the AIJ Standard for Loads and External Forces on Buildings and Structures, the National Building Code of Canada, and the method suggested by Ohkuma and co-workers. The values of estimated response acceleration correspond to the values of the full-scale measurements.

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Article

Several years of observations of accelerations during moderate to high wind at the Commerce Court Tower in Toronto, Canada, are presented and the effect of torsion in the upper stories is shown. Model and full-scale observations of the standard deviation of acceration correlate well for most wind directions. Implications for structural design using wind tunnel tests or a Code-based calculation method are discussed.

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Article

Full-scale measurements on the Great Belt East suspension bridge were carried out. Large amplitudes due to vortex-induced oscillations were measured, and lock-in observed. To the author's knowledge, pressures at the deck surface and accelerations are measured simultaneously for the first time, with the purpose of obtaining data which could contribute to further understanding of the fluid–structure interaction behaviour. Pressure–acceleration correlations at and off lock-in are estimated. Limitations of conventional experimental methods for predicting full-scale behaviour are evident, due to scale effects. Suggestions are made for improvements to the current design method for long-span bridges.

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Article

The acceleration potential method is introduced as a powerful approach to develop computational tools for aerodynamic calculations on horizontal axis windturbine rotors. The basic equations are given as well as a general analytical first-order asymptotic solution. Three computer codes are described in some detail as well as their application. In its simplest appearance the method is equivalent to a lifting line method with a wake relaxing in axial direction. The code in which this model is implemented, PREDICHAT, has been used extensively for calculations of performance and (stationary) blade loads. A more elaborated code, VIAX, has been developed specifically for the calculation of axial velocities in the near wake. Finally an approach is presented for the computation of loads under dynamic inflow conditions. Some results of the various codes are presented.

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Article

Several pedestrian wind comfort criteria have been suggested to help city planners and architects evaluate the safety and comfort of locations around planned developments. The criteria are based on the percent time certain wind speeds are exceeded annually but differ in implementation. To describe the relative behavior of the criteria, wind tunnel measurements of pedestrian wind speeds for nine building projects have been evaluated against five criteria: Melbourne (1978), Hunt, et.al. (1976), Penwarden and Wise (1975), Lawson and Penwarden (1975), and Isyumov and Davenport (1975). Measurements were made for 246 locations and were compared to the criteria. Differences among the criteria are evident, with that of Melbourne (1978) being more restrictive than those of Lawson and Penwarden (1975) and of Isyumov and Davenport (1975). Elevated turbulence intensities found near high-rise structures and the differing usage of mean and peak winds partially account for the differences.

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Article

A box-girder bridge extending about 700 m in length from the projected Kansai International Airport to constitute nearly one-fifth of a connecting bridge now on the drawing board is being designed as a combination of roadway bridge and railway bridge.Supported at about 100 m intervals, two roadway bridges run in parallel with each other with the railway bridge in between, thus making up triple runs of bridges together. The railway bridge in the middle changes its elevation relative to the flanking roadway bridges along the way.When designing the box-girder bridge, a series of wind tunnel tests were conducted using bridge models to evaluate the aerodynamic stability of the bridge, considering the fact that the box-girder bridge, though relatively short in its span, would essentially consist of the three bridges standing side by side 1),2). The wind tunnel test is still going on, and the authors review in their paper the results of structural response test which were obtained using the models representing local cross sectional structures of individual bridges.

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Article

This paper presents a method for quantifying accident risk for vehicles in high winds, a physical problem for which there are a large number of independent variables. In particular the parameters that specify driver behaviour are almost impossible to quantify with any precision. Also there are several interrelated failure modes for the driver/vehicle system. The method that is described is essentially based on an extensive series of computations for different pairs of these driver parameters, that enables the areas of safety within the driver parameter plane to be determined. The variation of this area of safety with both vehicle speed and wind speed is investigated, using both time domain and frequency domain models. Suggestions are made as to how this method might be used to determine accident risk for other problems within the field of wind engineering.

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Article

Currently, there are very few systematic analyses of vehicle performance on bridges in windy environments. There are thus no scientific data to support bridge management in this regard, such as when to close traffic on bridges. This paper presents a framework of vehicle accident analysis model on long-span bridges in windy environments. In the accompanying paper, a three-dimensional analysis of the coupled bridge–vehicle–wind system is developed. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers. Dynamic interaction analysis is then conducted on the vehicle–bridge system to predict the “global” bridge and vehicle dynamic responses without considering accident occurrences. The results of the global bridge–vehicle vibrations serve as the basis for the present accident analysis of the “local” vehicle vibrations. With the global vibrations as inputs of the accident model, the lateral response, yaw response of the vehicle, and the reaction forces of each individual wheel are obtained and the stability condition of the vehicles are analyzed. The vehicle accidents on long-span bridges are then identified with given accident criteria. The developed framework can be used in not only analyzing the vehicle performance on highways and on bridges, but also in predicting useful information for emergency preparedness agencies in developing evacuation plans.

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Article

A general probabilistic model for assessment of road vehicle accidents in windy environments is presented. The limit states of safe performance are outlined and the accident point is defined in the space of basic variables. The probability of accident is evaluated using a so-called safety index approach. The theory outlined is used to analyse a particular bus accident by setting up scenarios based on available information. The methodology presented has several potential applications, such as in accident analysis, and in improving the design of roads and highways by pointing out potential accident spots as well as in devising preventive measures to improve traffic safety in windy environments.

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