• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.227-230
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• 2007

SAR의 마이크로파를 이용하면 악 기상환경 및 주야간에도 해양의 관측이 가능하다. SAR의 해양표면에 대한 영상은 표면바람장과 관련된 대기적 현상에 관한 많은 정보를 가지고 있다. SAR로부터 추출되는 풍속의 정보는 다양하게 이용된다. SAR 영상으로부터 해상풍을 산출하기 위해서는 바람산출모델에 SAR 영상으로부터 추출한 풍향 자료와 후방산란계수 값을 입력하여 풍속을 산출한다. SAR 영상으로부터 구한 파향 스펙트럼은 항상 파향에 있어서 $180^{\circ}$의 상반된 두 정점을 보여주는데 이는 영상에 적용한 2차원 FFT의 결과이다. 파향에 있어서의 이러한 모호성은 육지의 위치라든지, 바람의 방향 혹은 수치모델 결과 등을 이용하여 결정하여야 한다. 이전에는 ENV14.0 을 이용해서 RadarSat-1 SAR 영상으로부터 DN 값을 추출한 후 다시 SN(Sigma Nought)으로 변환하는 것은 각각의 파일들을 수동적으로 처리를 해야 했기 때문에 많은 시간이 들었다. 이러한 수동적인 작업을 프로그램을 작성해서 SN(Sigma Nought) 값으로 변환을 하였다. 그 후 SN(Sigma Nought)로부터 풍향을 산출하는 과정에 있으며, 현재 풍향은 $180^{\circ}$의 모호성을 갖고 있기 때문에 좀 더 연구가 필요한 상황이다.

• 동아시아경상학회지
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• 제3권3호
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• pp.14-26
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• 2015

A wind speed forecast is a crucial and sophisticated task in a wind farm for planning turbines and corresponds to an estimate of the expected production of one or more wind turbines in the near future. By production is often meant available power for wind farm considered (with units KW or MW depending on both the wind speed and direction. Such forecasts can also be expressed in terms of energy, by integrating power production over each time interval. In this study, we technically focused on mathematical modeling of wind speed and direction forecast based on locally data set gathered from Aghdasiyeh station in Tehran. The methodology is set on using most common techniques derived from literature review. Hence we applied the most sophisticated forecasting methods to embed seasonality, trend, and irregular pattern for wind speed as an angular variables. Through this research, we carried out the most common techniques such as the Box and Jenkins family, VARMA, the component method, the Weibull function and the Fourier series. Finally, the best fit for each forecasting method validated statistically based on white noise properties and the final comparisons using residual standard errors and mean absolute deviation from real data.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.558-565
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• 2013

This paper presents how to determine AEP(Annual Energy Production) by a small wind turbine in DuckjeokDo island. Evaluation of AEP is introduced to make a self-contained island including renewable energy sources of wind, solar, and tidal energy. To determine the AEP in DuckjeokDo island, a local wind data is analyzed using the annual wind data from Korea Institute of Energy Research firstly. After the wind data is separated in 12-direction, a mean wind speed at each direction is determined. And then, a small wind turbine power curve is selected by introducing the capacity of a small wind turbine and the energy production of the wind turbine according to each wind direction. Finally, total annual wind energy production for each small wind turbine can be evaluated using the local wind density and local energy production considering a mechanical energy loss. Throughout the analytic study, it is found that the AEP of DuckjeokDo island is about 2.02MWh/y and 3.47MWh/y per a 1kW small wind turbine installed at the altitude of 10 m and 21m, respectively.

• KIEAE Journal
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• 제4권3호
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• pp.195-202
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• 2004

This study focuses on the impacts of apartment building arrangements on the outdoor and indoor air quality - the efficiency of natural ventilation in the outside/inside area of an apartment with consideration to the characteristics of an air flow in outside area depending on the types of the arrangements, the main direction of the wind, and the outside wind pressure on the building facade. As indices to evaluate the efficiency of natural ventilation, the concepts of "Age of Air" and "Purging Flow Rate(PFR)" were used in this study. As indices to classify the efficiency of indoor natural ventilation, the mean values of the wind pressure differences between the front and the back elevations of an apartment building were used. The research showed that the PFR of each apartment building arrangement ranges from 0.867 to 3.253. The "minus-shaped" arrangement showed the highest PFR, 2.306; the "zigzag-shaped" arrangement measured 1.889; the "angle-shaped" arrangement measured 1.465, and the "square-shaped" arrangement measured 1.241. Depending on the direction of the wind, the pressure differences range extremely, with variations from 170% to 2300%. Thus, the indoor natural ventilation efficiency can be changed by the pressure differences of the wind, which are sensitive to the main direction of the wind even though the structure and planning of the apartment complexes are the same. Despite the same direction of the wind, even the efficiency can be diverse. This study showed how to predict the most beneficial apartment building arrangement for the profitable natural ventilation efficiency in each direction of the wind.

• Wind and Structures
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• 제35권4호
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• pp.229-242
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• 2022

Wind tunnel test is often adopted to assess the site-specific wind characteristics for the design of bridges as suggested by current design standards. To investigate the wind characteristics of flat and mountainous terrain, two topographic models are tested in a boundary layer wind tunnel. The wind characteristics, including the vertical and horizontal mean wind speed distributions, the turbulence intensity, and the wind power spectra, are presented. They are investigated intensively in present study with the discussions on the effect of wind direction and the effect of topography. It is indicated that for flat terrain, the wind direction has negligible effect on the wind characteristics, however, the assumption of a homogenous wind field for the mountainous terrain is not applicable. Further, the non-homogeneous wind field can be defined based on a proposed approach if the wind tunnel test or on-site measurement is performed. The calculated turbulence intensities and wind power spectra by using the measured wind speeds are also given. It is shown that for the mountainous terrain, engineers should take into account the variability of the wind characteristics for design considerations.

• 한국대기환경학회지
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• 제8권2호
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• pp.138-145
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• 1992

Dependence of the standard deviation of wind direction fluctuations, ${\sigma}_{\theta}$, on atmospheric stability, averaging time and topography were analysed with the data measured at three sites, Youngjongdo beach of the Yellow Sea, Chuncheon basin and Doam-Dam valley. The results show that the mean value of ${\sigma}_{\theta}$ is large in complex terrain, the Doam-Dam site. It is notable that the large value of ${\sigma}_{\theta}$ at night is associated with the low wind speed and the strong stable condition. In order to study the long-period fluctuations of the wind direction, ${\sigma}_{\theta}$ for longer than 10 minutes averaging time was further analysed using the data obtained at the Chuncheon basin. At the averaging time shorter than 60 minutes, larger ${\sigma}_{\theta}$ is associated with longer averaging time in the strong stable condition. However, ${\sigma}_{\theta}$ was not affected significantly by wind speed and averaging time in neutral conditions. The results of the spectrum analysis for the time series data of wind direction showed that low-frequency fluctuations ranging from 10 to 60 minutes were dominated at the Chuncheon basin in strong stable condition.

• 환경영향평가
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• 제20권4호
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• pp.557-564
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• 2011

This study was conducted to investigate the sudden rise of fine particle concentration after the passage of typhoon USAGI and NARI in Busan. Nocturnal inversion layer was formed at atmospheric boundary layer and wind direction changed from southerly wind to northeasterly wind after USAGI passed through Busan. Fine particle concentration in Busan rapidly increased by subsidence of air pollutants released from sources and dust transported from in the vicinity of industrial regions. Wind direction changed from northeasterly wind to southeasterly wind, wind velocity increased and lower atmosphere became extremely unstable after NARI passed through Busan. $PM_{10}$ concentration of Busan increased sharply because of surface dust dispersed by strong wind. Fine particle concentration generally decreases by precipitation and wind after typhoon passes through. However, the concentration can also go up not only by subsidence and transportation in nocturnal inversion layer but also by surface dust which temporarily occurs by strong wind.

• Wind and Structures
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• 제29권6호
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• pp.471-488
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• 2019

Wind pressure is a critical argument for the wind-resistant design of structures. The attempt, however, to explore the wind pressure field on buildings still encounters challenges though a large body of researches utilizing wind tunnel tests and wind field simulations were carried out, due to the difficulty in logical treatments on the scale effect and the modeling error. The full-scale measurement has not yet received sufficient attention. By performing a field measurement, the present paper systematically addresses wind pressures on the rectangular attic of a double-tower building. The spatial and temporal correlations among wind speed and wind pressures at measured points are discussed. In order to better understand the wind pressure distribution on the attic facades and its relationship against the approaching flow, a full-scale CFD simulation on the similar rectangular attic is conducted as well. Comparative studies between wind pressure coefficients and those provided in wind-load codes are carried out. It is revealed that in the case of wind attack angle being zero, the wind pressure coefficient of the cross-wind facades exposes remarkable variations along both horizontal and vertical directions; while the wind pressure coefficient of the windward facade remains stable along horizontal direction but exposes remarkable variations along vertical direction. The pattern of wind pressure coefficients, however, is not properly described in the existing wind-load codes.

• Wind and Structures
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• 제31권3호
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• pp.217-227
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• 2020

Based on translation models, both Gaussian and non-Gaussian wind fields are generated using spectral representation method for investigating the influence of non-Gaussian characteristics and directivity effect of wind load on fatigue damage of wind turbine. Using the blade aerodynamic model and multi-body dynamics, dynamic responses are calculated. Using linear damage accumulation theory and linear crack propagation theory, crack initiation life and crack propagation life are discussed with consideration of the joint probability density distribution of the wind direction and mean wind speed in detail. The result shows that non-Gaussian characteristics of wind load have less influence on fatigue life of wind turbine in the area with smaller annual mean wind speeds. Whereas, the influence becomes significant with the increase of the annual mean wind speed. When the annual mean wind speeds are 7 m/s and 9 m/s at hub height of 90 m, the crack initiation lives under softening non-Gaussian wind decrease by 10% compared with Gaussian wind fields or at higher hub height. The study indicates that the consideration of the influence of softening non-Gaussian characteristics of wind inflows can significantly decrease the fatigue life, and, if neglected, it can result in non-conservative fatigue life estimates for the areas with higher annual mean wind speeds.

• Wind and Structures
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• 제23권3호
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• pp.191-209
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• 2016

Wind tunnel tests of a 1/2200-scale mountainous terrain model have been carried out to investigate local wind characteristics at a bridge location in southeast Tibet, China. Flows at five key locations on the bridge at deck level were measured for 26 directions. It was observed that wind characteristics (including mean wind velocity and overall turbulence intensity) vary significantly depending on the approaching wind direction and measurement position. The wind inclination angle measured in the study fluctuated between $-18^{\circ}$ and $+16^{\circ}$ and the ratio of mean wind velocity to reference wind velocity was small when the wind inclination angles were large, especially for positive wind inclination angles. The design standard wind speed and the minimum critical wind speed for flutter rely on the wind inclination angle and should be determined from the results of such tests. The variation of wind speed with wind inclination angles should be of the asymmetry step type. The turbulence characteristics of the wind were found to be similar to real atmospheric flows.