• Wind and Structures
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• v.10 no.2
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• pp.153-176
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• 2007

The Proper Orthogonal Decomposition (POD) is a statistical method particularly suitable and versatile for dealing with many problems concerning wind engineering and several other scientific and humanist fields. POD represents a random process as a linear combination of deterministic functions, the POD modes, modulated by uncorrelated random coefficients, the principal components. It owes its popularity to the property that only few terms of the series are usually needed to capture the most energetic coherent structures of the process, and a link often exists between each dominant mode and the main mechanisms of the phenomenon. For this reason, POD modes are normally used to identify low-dimensional subspaces appropriate for the construction of reduced models. This paper provides a state-of-the-art and some prospects on POD, with special regard to its framework and applications in wind engineering. A wide bibliography is also reported.

• Journal of Wind Energy
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• v.10 no.3
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• pp.5-11
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• 2019

This paper suggests and compares two algorithms, a moving average filter method and a method developed by the National Renewable Energy Laboratory (NREL), to verify the yaw control algorithm characteristic to reduce yaw error for a wind turbine. A characteristic change for yaw movement in accordance with control parameter change that consists of each control method has been verified. Also, yaw simulations were performed using nacelle wind data measured from two areas with different turbulence intensities and the yaw movement data in each area was compared. These two algorithms and real data were compared by calculating mean absolute error (MSE) and the number of yawing (NY). As a result of the analysis, the MSE values were not significantly different between the two algorithms, but the algorithm proposed by the NREL was found to reduce yaw movement by up to 50 percent more than the moving average filter method.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.131-138
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• 2003

This paper considered the structural mechanism of transitional boundary layer by the experimental approach. In order to measure the turbulence quantity in the boundary layer, we made a wind tunnel with 400${\times}$190${\times}$2500 mm test section and a flat plate with well fabricated leading edge. Hot wire anemometer was used for acquiring the continuous turbulence signal which is processed by special software. The results of experiment show that the region where turbulence spot is dominant moves from near wall to overall layer and thus the anisotropy of velocity fluctuation shows so large value. Also the turbulence energy originally contained in low frequency band comes up to the high frequency band. Finally the turbulence model needs minimum two length scales to consider the pre-transition region.

• Wind and Structures
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• v.5 no.1
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• pp.49-60
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• 2002

This paper describes a simple method for evaluating the design wind loads for the structural frames of circular flat roofs with long spans. The dynamic response of several roof models were numerically analyzed in the time domain as well as in the frequency domain by using wind pressure data obtained from a wind tunnel experiment. The instantaneous displacement and bending moment of the roof were computed, and the maximum load effects were evaluated. The results indicate that the wind-induced oscillation of the roof is generally dominated by the first mode and the gust effect factor approach can be applied to the evaluation of the maximum load effects. That is, the design wind load can be represented by the time-averaged wind pressure multiplied by the gust effect factor for the first mode. Based on the experimental results for the first modal force, an empirical formula for the gust effect factor is provided as a function of the geometric and structural parameters of the roof and the turbulence intensity of the approach flow. The equivalent design pressure coefficients, which reproduce the maximum load effects, are also discussed. A simplified model of the pressure coefficient distribution is presented.

• Wind and Structures
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• v.9 no.5
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• pp.387-396
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• 2006

This paper presents the wind characteristics of Typhoon Dujuan as measured at a 50 m guyed mast in Hong Kong. The basic wind speed, wind direction and turbulent intensity are studied at two measurement levels of the structure. The power spectral density of the typhoon is compared with the von Karman prediction, and the coherence between wind speeds at the two measurement levels is found to This paper presents the wind characteristics of Typhoon Dujuan as measured at a 50 m guyed mast in Hong Kong. The basic wind speed, wind direction and turbulent intensity are studied at two measurement levels of the structure. The power spectral density of the typhoon is compared with the von Karman prediction, and the coherence between wind speeds at the two measurement levels is found to compare with Davenport's prediction. The effect of typhoon Dujuan on the response of the structure will be discussed in a companion paper (Law, et al. 2006).with Davenport's prediction. The effect of typhoon Dujuan on the response of the structure will be discussed in a companion paper (Law, et al. 2006).

• Structural Engineering and Mechanics
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• v.10 no.6
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• pp.545-559
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• 2000

A Wind and Structural Health Monitoring System (WASHMS) has been installed in the Tsing Ma suspension Bridge in Hong Kong with one of the objectives being the verification of analytical processes used in wind-resistant design. On 2 August 1997, Typhoon Victor just crossed over the Bridge and the WASHMS timely recorded both wind and structural response. The measurement data are analysed in this paper to obtain the mean wind speed, mean wind direction, mean wind inclination, turbulence intensity, integral scale, gust factor, wind spectrum, and the acceleration response and natural frequency of the Bridge. It is found that some features of wind structure and bridge response are difficult to be considered in the currently used analytical process for predicting buffeting response of long suspension bridges, for the Bridge is surrounded by a complex topography and the wind direction of Typhoon Victor changes during its crossing. It seems to be necessary to improve the prediction model so that a reasonable comparison can be performed between the measurement and prediction for long suspension bridges in typhoon prone regions.

• Wind and Structures
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• v.18 no.5
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• pp.567-598
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• 2014

In this paper, wind induced aerodynamic loads on a standard tall building have been evaluated through large-eddy simulation (LES) technique. The flow parameters of an open terrain were recorded from the downstream of an empty boundary layer wind tunnel (BLWT) and used to prescribe the transient inlet boundary of the LES simulations. Three different numerically generated inflow boundary conditions have been investigated to assess their suitability for LES. A high frequency pressure integration (HFPI) approach has been employed to obtain the wind load. A total of 280 pressure monitoring points have been systematically distributed on the surfaces of the LES model building. Similar BLWT experiments were also done to validate the numerical results. In addition, the effects of adjacent buildings were studied. Among the three wind field generation methods (synthetic, Simirnov's, and Lund's recycling method), LES with perturbation from the synthetic random flow approach showed better agreement with the BLWT data. In general, LES predicted peak wind loads comparable with the BLWT data, with a maximum difference of 15% and an average difference of 5%, for an isolated building case and however higher estimation errors were observed for cases where adjacent buildings were placed in the vicinity of the study building.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.94-101
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• 2012

A Dokdo wind resource map has been drawn up for the Green Island Energy Master Plan according to Korea's national vision for 'Low Carbon Green Growth'. The micro-siting software WindSim v5.1,which is based on Computational Flow Analysis, is used with MERRA reanalysis data as synoptic climatology input data, and sensitivity analysis on turbulence model is accompanied. A wind resource assessment has been conducted for the Dokdo wind power dissemination plan, which consists of two 10kW wind turbines to be installed at the Dongdo dock and Dokdo guard building. It is evaluated that the capacity factors at Dongdo dock and Dokdo guard building are about 20% and 30% respectively, and annual and hourly variations of wind power generation have been analyzed, but summertime energy production is predicted to be only 40% of wintertime energy production.

• Wind and Structures
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• v.2 no.1
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• pp.1-23
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• 1999

Wind effects are critical considerations in the design of topside structures, overall structural systems, or both, depending on the water depth and type of offshore platform. The reliable design of these facilities for oil fields in regions of hostile environment can only be assured through better understanding of the environmental load effects and enhanced response prediction capabilities. This paper summarizes the analysis and performance of offshore platforms under extreme wind loads, including the quantification of wind load effects with focus on wind field characteristics, steady and unsteady loads, gust loading factors, application of wind tunnel tests, and the provisions of the American Petroleum Institute Recommended Practice 2A - Working Stress Design (API RP 2A-WSD) for the construction of offshore structures under the action of wind. A survey of the performance of platforms and satellite structures is provided, and failure mechanisms concerning different damage scenarios during Hurricane Andrew are examined. Guidelines and provisions for improving analysis and design of structures are addressed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.366-371
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• 2003

농촌지역의 인구가 급속히 감소하고 있는 가운데, 농촌인력의 노약화, 여성화가 매우 빠르게 진행되고 있다. 인력을 효율적으로 이용하고 농업생산성을 높이기 위하여 현재 온실, 축사 등 농업시설은 자동화, 대형화되어 가고 있는 추세에 있다. 이러한 농업시설의 대형화에 따른 최적환경조성의 중요성이 대두되고 있어서 이에 따른 적합한 시설환경이 요구되고 있으나 적정환기가 이루어지지 않아 생산성 향상에 어려움이 많이 있다. (중략)