• Wind and Structures
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• v.10 no.3
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• pp.249-268
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• 2007

Past experience indicates that the majority of failures of electrical transmission tower structures occurred during high intensity wind events, such as downbursts. The wind load distribution associated with these localized events is different than the boundary layer wind profile that is typically used in the design of structures. To the best of the authors' knowledge, this study represents the first comprehensive investigation that assesses the effect of varying the downburst parameters on the structural performance of a transmission line structure. The study focuses on a guyed tower structure and is conducted numerically using, as a case study, one of the towers that failed in Manitoba, Canada, during a downburst event in 1996. The study provides an insight about the spatial and time variation of the downburst wind field. It also assesses the variation of the tower members' internal forces with the downburst parameters. Finally, the structural behaviour of the tower under critical downburst configurations is described and is compared to that resulting from the boundary layer normal wind load conditions.

• Atmosphere
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• v.31 no.4
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• pp.405-420
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• 2021

Forest fire happens every year at Yeongdong, Gangwon-do, due to the strong local wind during the spring time and it causes a huge damage. This wind is named "Yangganjipung" or "Yanggangjipung" that blows along Yeongdong. However, the occurrence conditions of the wind have been still unclear. To identify the occurrence mechanism of local strong wind through three-dimensional observation data, Gangwon Regional Meteorological Administration performed Joint Gangwon-Yeongdong 3D Observation Project in 2020. The special observation was carried out for 6 times from March to April. The observation data was analyzed by focusing on the structure of synoptic pressure distribution and inversion layer. The result showed that the strength of wind is different depending on the latitude of low pressure, intensity of inversion layer, and changes on height in the south-high and north-low pressure distribution. As the interval of the upper and lower parts of the inversion layer was narrow, the strength of the wind became stronger, which is one of the observational characteristics of the springtime wind pattern at Yeongdong, Gangwon-do. In future, the clear mechanism of the local wind in the Yeongdong during the spring time is expected to be verified based on the accumulative observation data and close analysis.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.135-145
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• 2023

Developing high-fidelity Computational Fluid Dynamics (CFD) simulation methods used to evaluate the airwake characteristics along a flight deck of a large ship, the various kind of data such as actual ship measurement and wind tunnel results are required to verify the accuracy of CFD simulation. Inflow velocity profile at the bow, local unsteady flow field data around the flight deck, and highly reliable wind tunnel data which were measured after reviewing Atmospheric Boundary Layer (ABL) simulation and Reynolds Number effects were also used to determine the key parameters such as turbulence model, time resolution and accuracy, grid resolution and type, inflow condition, domain size, simulation length, and so on in STAR CCM⁺. Velocity ratio and turbulent intensity difference between Full-scale CFD and actual ship measurement at the measurement points show less than 2% and 1.7% respectively. And differences in velocity ratio and turbulence intensity between wind tunnel test and small-scale CFD are both less than 2.2%. Based upon this fact, the selected parameters in CFD simulation are highly reliable for a specific wind condition.

• Wind and Structures
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• v.10 no.4
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• pp.315-346
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• 2007

A preceding companion article introduced the slot jet approach for large-scale quasi-steady modelling of a downburst outflow. This article extends the approach to model the time-dependent features of the outflow. A two-dimensional slot jet with an actuated gate produces a gust with a dominant roll vortex. Two designs for the gate mechanism are investigated. Hot-wire anemometry velocity histories and profiles are presented. As well, a three-dimensional, subcloud numerical model is used to approximate the downdraft microphysics, and to compute stationary and translating outflows at high resolution. The evolution of the horizontal and vertical velocity components is examined. Comparison of the present experimental and numerical results with field observations is encouraging.

• Wind and Structures
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• v.20 no.3
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• pp.469-488
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• 2015

A full-scale instrumented low-rise building with gable roof was built at a coastal site with a high incidence of tropical cyclones for monitoring of wind effects on the building during windstorms. This paper presents the field measurements of the wind velocity field around and the wind-induced pressures on the low-rise building during the passage of severe tropical storm Soudelor. Near-ground wind characteristics such as wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and wind velocity spectra were investigated. The wind-induced pressures on the roof of the building were analyzed and discussed. The results revealed that the eave and ridge edges on the roof were subjected to the most severe suction pressures under quartering winds. These suction pressures showed obvious non-Gaussian behavior. The measured results were compared with the provisions of ASCE 7-10 to assess the suitability of the code of practice for the wind-resistant design of low-rise buildings under tropical cyclones. The field study aims to provide useful information that can enhance our understanding of the extreme wind effects on low-rise buildings in an effort to reduce tropical cyclone wind damages to residential buildings.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.104-114
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• 1997

This study was carried out to research the influence of climatic conditions including wind direction, wind speed on air pollution in Seoul. The data were obtained from the 4 sites of air pollution monitoring stations in Seoul from '95 to '96, and analyzed statistically by SAS program. The results were as follows 1. The prevailing wind directions by season in each site were as follows Nangajwa-dong were showed SE in spring, fall, winter and WNW in summer. Ssangmun-dong were showed NW in spring, fall, winter and NNE in summer. Kuro-dong were showed SW in spring, summer, ENE in fall and NW in winter. Bangi-dong were showed WNW in four seeasons. 2. The concentrations of 5 kinds(SO$_2$, Dust, NO$_2$, CO, THC) of air pollutants were relatively low in west wind. In case of O$_3$ was opposite. 3. The concentrations of 5 kinds of air pollutants were increase with decreasing wind speeds. 4. The washing effects of air pollution by rain were significant. The concentrations of 5 kinds of air pollutants were high when the humidity were 61-80%, and low as it were 0-20%. In case of O$_3$ was opposite. 5. All of air pollutants concentrations but O$_3$ were high when the UV intensity level and temperature within the range of above zero were low level.

• Wind and Structures
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• v.39 no.2
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• pp.111-123
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• 2024

The atmospheric turbulence characteristics measured at a meteorological station in northwest part of the Czech Republic are presented for selected time periods in the year 2017. The terrain of this region is influenced by surface coal mining and the related industry. The datasets used in this study were measured using four ultrasonic anemometers installed on an 80 m high meteorological mast at heights of 20, 40, 60 and 80 m, respective. From the primary high-frequency datasets, time intervals in order of hours were selected and integral turbulence characteristics (ITCs), turbulence intensities and turbulence spectra were analyzed. The time intervals were selected with respect to atmospheric stability parameter, known as Obukhov number. We concentrated on the days with higher wind velocity and neutral atmospheric stratification. The wind characteristics investigated in this study include the wind speed, wind direction and its histograms, turbulence intensity, friction velocity and wind power spectra. The ITCs and spectral characteristics were compared with the theoretical models and values from the literature. The resulting ITCs showed the values for urban locations similar to those found in other studies and can be used in practical design. The computed turbulence spectra followed the shape of theoretical spectra of turbulence for both horizontal and vertical velocity components. The computed integral length scales have shown to be unsuitable for further use due to their highly scattered values.

• Wind and Structures
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• v.22 no.1
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• pp.65-87
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• 2016

The wind velocity profile over the height of a structure in high intensity wind (HIW) events, such as downbursts, differs from that associated with atmospheric boundary layer (ABL) winds. Current design codes for lattice transmission structures contain only limited advice on the treatment of HIW effects, and structural design is carried out using wind load profiles and response factors derived for ABL winds. The present study assesses the load-deformation curve (capacity curve) of a transmission tower under modeled downburst wind loading, and compares it with that obtained for an ABL wind loading profile. The analysis considers nonlinear inelastic response under simulated downburst wind fields. The capacity curve is represented using the relationship between the base shear and the maximum tip displacement. The results indicate that the capacity curve remains relatively consistent between different downburst scenarios and an ABL loading profile. The use of the capacity curve avoids the difficulty associated with defining a reference wind speed and corresponding wind profile that are adequate and applicable for downburst and ABL winds, thereby allowing a direct comparison of response under synoptic and downburst events. Uncertainty propagation analysis is carried out to evaluate the tower capacity by considering the uncertainty in material properties and geometric variables. The results indicated the coefficient of variation of the tower capacity is small compared to those associated with extreme wind speeds.

• Wind and Structures
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• v.17 no.6
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• pp.609-627
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• 2013

The Yingxian wooden tower in China is currently the tallest wooden tower in the world. It was built in 1056 AD and is 65.86 m high. Field measurements of wind speed and wind-induced response of this tower are conducted. The wind characteristics, including the average wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and velocity spectrum are investigated. The power spectral density and the root-mean-square wind-induced acceleration are analyzed. The structural modal parameters of this tower are identified with two different methods, including the Empirical Mode Decomposition (EMD) combined with the Random Decrement Technique (RDT) and Hilbert transform technique, and the stochastic subspace identification (SSI) method. Results show that strong wind is coming predominantly from the West-South of the tower which is in the same direction as the inclination of the structure. The Von Karman spectrum can describe the spectrum of wind speed well. Wind-induced torsional vibration obviously occurs in this tower. The natural frequencies identified by EMD, RDT and Hilbert Transform are close to those identified by SSI method, but there is obvious difference between the identified damping ratios for the first two modes.

• Wind and Structures
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• v.34 no.2
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• pp.231-257
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• 2022

Transmission lines systems are important components of the electrical power infrastructure. However, these systems are vulnerable to damage from high wind events such as hurricanes. This study presents the results from a 1:50 scale aeroelastic model of a multi-span transmission lines system subjected to simulated hurricane winds. The transmission lines system considered in this study consists of three lattice towers, four spans of conductors and two end-frames. The aeroelastic tests were conducted at the NSF NHERI Wall of Wind Experimental Facility (WOW EF) at the Florida International University (FIU). A horizontal distortion scaling technique was used in order to fit the entire model on the WOW turntable. The system was tested at various wind speeds ranging from 35 m/s to 78 m/s (equivalent full-scale speeds) for varying wind directions. A system identification (SID) technique was used to evaluate experimental-based along-wind aerodynamic damping coefficients and compare with their theoretical counterparts. Comparisons were done for two aeroelastic models: (i) a self-supported lattice tower, and (ii) a multi-span transmission lines system. A buffeting analysis was conducted to estimate the response of the conductors and compare it to measured experimental values. The responses of the single lattice tower and the multi-span transmission lines system were compared. The coupling effects seem to drastically change the aerodynamic damping of the system, compared to the single lattice tower case. The estimation of the drag forces on the conductors are in good agreement with their experimental counterparts. The incorporation of the change in turbulence intensity along the height of the towers appears to better estimate the response of the transmission tower, in comparison with previous methods which assumed constant turbulence intensity. Dynamic amplification factors and gust effect factors were computed, and comparisons were made with code specific values. The resonance contribution is shown to reach a maximum of 18% and 30% of the peak response of the stand-alone tower and entire system, respectively.