• Wind and Structures
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• 제23권6호
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• pp.577-594
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• 2016

In this paper a practical modelling methodology is presented for a series of aero- servo- elastic- coupled numerical analyses of small wind turbine operation, with particular emphasis on variable speed generator modelling in various wind speed conditions. The following characteristics are determined using the available computer tools: the tip speed ratio as a function of the generator constant (under the assumption of constant wind speed), the turbine coefficient of power as a function of the tip speed ratio (the torque curve is modified accordingly and generator speed and power curves are plotted), turbine power curves and coefficient of power curve as functions of the incoming wind speed. The last stage is to determine forces and torques acting on rotor blades and turbine tower for specific incoming wind speeds in order to examine the impact of the stall phenomena on these values (beyond the rated power of the turbine). It is shown that the obtained results demonstrate a valuable guideline for small wind turbines design process.

• 물과 미래
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• 제20권2호
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• pp.127-138
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• 1987

서해지역에서 해안구조물을 위한 설계파는 연안지상측후소의 과거 풍속자료로부터 해상풍의 설계풍속을 산정하고 지역별로 결정되는 취송역으로부터 파랑예측모델을 이용하여 결정하는 방법이 제안되었다. 서해에서 설계파를 지배하는 바람은 북서방향(W~N)의 동기계절풍과 남서(WSW~S) 방향의 하기계절풍 및 태풍이며 해상풍의 풍속은 U$\geq$20m/s의 탄풍에 대하여 연안의 지상풍속의 0.8~0.9배를 나타낸다. 서해의 해안지역은 그 위치여건에 따라 세 지역으로 구분할 수 있으며 각각의 지역에 대하여 설계파산정을 위한 취송역을 결정할 수 있다. 수정된 S.M.B. 법에 의하면 서해지역에서 100년빈도 설계파의 심해유의파고는 4.4m~8.3m, 주기는 8.9초~12.0초의 범위를 보인다.

• Wind and Structures
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• 제26권3호
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• pp.129-146
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• 2018

Extreme wind speed analysis has been carried out conventionally by assuming the extreme series data is stationary. However, time-varying trends of the extreme wind speed series could be detected at many surface meteorological stations in China. Two main reasons, exposure change and climate change, were provided to explain the temporal trends of daily maximum wind speed and annual maximum wind speed series data, recorded at Hangzhou (China) meteorological station. After making a correction on wind speed series for time varying exposure, it is necessary to perform non-stationary statistical modeling on the corrected extreme wind speed data series in addition to the classical extreme value analysis. The generalized extreme value (GEV) distribution with time-dependent location and scale parameters was selected as a non-stationary model to describe the corrected extreme wind speed series. The obtained non-stationary extreme value models were then used to estimate the non-stationary extreme wind speed quantiles with various mean recurrence intervals (MRIs) considering changing climate, and compared to the corresponding stationary ones with various MRIs for the Hangzhou area in China. The results indicate that the non-stationary property or dependence of extreme wind speed data should be carefully evaluated and reflected in the determination of design wind speeds.

• 한국항공우주학회지
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• 제31권4호
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• pp.92-98
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• 2003

한양대학교 중형 아음속 풍동의 설계요구사항에 따라 균일도 증가 및 난류도 감소를 위한 최적설계를 수행하였다. 신뢰성 있는 풍동실험을 위해 먼저 풍동 시험부의 균일도와 난류강도 특성이 먼저 파악되어야 한다. 한양대학교 중형 아음속 풍동의 비균일도와 난류강도는 세 부분의 속도영역에서 피토관과 X형 열선프로브로 각각 측정되었다. 풍동 시험부의 유속이 증가함에 따라 비균일도가 작아졌으나 시험부의 측정단면이 확산부에 가까워질수록 비균일도가 크게 나타났다. 난류강도는 시험부 중앙에서 설계 요구조건에 비해 약간 높게 측정되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.521-524
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• 2009

This study describes aerodynamic noise of high speed wind turbine system, which is invented as a new concept in order to reduce the torque of main shaft, for design parameters of the rotor blade. For parametric study of high speed rotor aerodynamic noise, Unsteady Vortex Lattice Method with Nonlinear Vortex Correction Method is used for analysis of wind turbine blade aerodynamic and Farassat1A and Semi-Empirical are used for low frequency noise and airfoil self noise. Parameters are chord length, twist and rotational speed for this parametric research. In the low frequency range, the change of noise is predicted the same level as each parameters varies. However, in case of broadband noise of blade, the change of rotational speed makes more variation of noise than other parameters. When the geometric angles of attack are fixed, as the rotational speed is increased by 5RPM, the noise level is increased by 4dB.

• Wind and Structures
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• 제4권3호
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• pp.197-212
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• 2001

Observations of extreme wind speeds in the United Kingdom from 1970 to 1980, corrected for the influence of upwind ground roughness and topography, have been analysed using the recently-developed "Improved Method of Independent Storms" (IMIS). The results have been used to compile two new maps of base wind speed and to confirm the climatic factors in current use. One map is 'irrespective' of wind direction and the other is 'equally weighted' by direction. The 'equally weighted' map is expected to be more consistently reliable and appropriate for use with the climatic factors for the design of buildings and structures.

• Wind and Structures
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• 제13권3호
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• pp.275-292
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• 2010

Wind tunnel experiments were conducted to investigate the wind characteristics in the mountainous valley terrain with 4 simplified valley models and a 1:500 scale model of an existing valley terrain in the simulated atmospheric neutral boundary layer model. Measurements were focused on the mean wind flow and longitudinal turbulence intensity. The relationship between hillside slopes and the velocity speed-up effect were studied. By comparing the preliminary results obtained from the simplified valley model tests and the existing terrain model test, some fundamental information was obtained. The measured results indicate that it is inappropriate to describe the mean wind velocity profiles by a power law using the same roughness exponent along the span wise direction in the mountainous valley terrain. The speed-up effect and the significant change in wind direction of the mean flow were observed, which provide the information necessary for determining the design wind speed such as for a long-span bridge across the valley. The longitudinal turbulence intensity near the ground level is reduced due to the speed-up effect of the valley terrain. However, the local topographic features of a more complicated valley terrain may cause significant perturbation to the general wind field characteristics in the valley.

• 한국방재학회 논문집
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• 제9권4호
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• pp.21-28
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• 2009

국내 조선소는 빈번하게 태풍에 의해 영향을 받는 해안에 위치하며, 풍하중에 취약한 많은 경량 구조의 시설물들로 이루어져 있다. 본 연구에서는 주변 지형과 조선소내부 건물의 영향까지 고려하여 시설물의 강풍에 대한 위험 분석을 수행하였다. 몬테카를로 시뮬레이션에 의해 대상 지역의 극한 풍속을 추정하여 전산유체역학 해석을 위한 입사풍속으로 설정하였으며, 난류 유동을 고려한 전산 유체 해석을 이용하여 시설물 표면에 발생하는 풍압과 조선소 사업장 내의 풍속 분포를 추정하였다. 결과로서 일부 시설물에는 설계 하중보다 높은 풍하중이 작용하여 보강이 요구되는 것으로 판단되며, 향후 설계 풍하중을 고려하는 경우 주변의 국부적 지형 변화와 건물 배치를 고려해야 할 것으로 나타났다.

• Wind and Structures
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• 제26권6호
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• pp.383-395
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• 2018

An accurate determination of wind speed distribution is the basis for an evaluation of the wind energy potential required to design a wind turbine, so it is important to estimate unknown parameters of wind speed distribution. In this paper, Gumbel distribution is used in modelling wind speed data, and alternative robust estimation methods to estimate its parameters are considered. The methodologies used to obtain the estimators of the parameters are least absolute deviation, weighted least absolute deviation, median/MAD and least median of squares. The performances of the estimators are compared with traditional estimation methods (i.e., maximum likelihood and least squares) according to bias, mean square deviation and total mean square deviation criteria using a Monte-Carlo simulation study for the data with and without outliers. The simulation results show that least median of squares and median/MAD estimators are more efficient than others for data with outliers in many cases. However, median/MAD estimator is not consistent for location parameter of Gumbel distribution in all cases. In real data application, it is firstly demonstrated that Gumbel distribution fits the daily mean wind speed data well and is also better one to model the data than Weibull distribution with respect to the root mean square error and coefficient of determination criteria. Next, the wind data modified by outliers is analysed to show the performance of the proposed estimators by using numerical and graphical methods.

• Wind and Structures
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• 제13권1호
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• pp.1-20
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• 2010

The recommended factored design wind load effects for overhead lattice transmission line towers by codes and standards are evaluated based on the applicable wind load factor, gust response factor and design wind speed. The current factors and design wind speed were developed considering linear elastic responses and selected notional target safety levels. However, information on the nonlinear inelastic responses of such towers under extreme dynamic wind loading, and on the structural capacity curves of the towers in relation to the design capacities, is lacking. The knowledge and assessment of the capacity curve, and its relation to the design strength, is important to evaluate the integrity and reliability of these towers. Such an assessment was performed in the present study, using a nonlinear static pushover (NSP) analysis and incremental dynamic analysis (IDA), both of which are commonly used in earthquake engineering. For the IDA, temporal and spatially varying wind speeds are simulated based on power spectral density and coherence functions. Numerical results show that the structural capacity curves of the tower determined from the NSP analysis depend on the load pattern, and that the curves determined from the nonlinear static pushover analysis are similar to those obtained from IDA.