• Wind and Structures
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• 제12권4호
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• pp.383-400
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• 2009

Low rise building roofs can be subjected to large fluctuating pressures during a tropical cyclone resulting in fatigue failure of cladding. Following the damage to housing in Tropical Cyclone Tracy in Darwin, Australia, the Darwin Area Building Manual (DABM) cyclic loading test criteria, that loaded the cladding for 10000 cycles oscillating from zero to a permissible stress design pressure, and the Experimental Building Station TR440 test of 10200 load cycles which increased in steps to the permissible stress design pressure, were developed for assessing building elements susceptible to low cycle fatigue failure. Recently the 'Low-High-Low' (L-H-L) cyclic test for metal roofing was introduced into the Building Code of Australia (2007). Following advances in wind tunnel data acquisition and full-scale wind loading simulators, this paper presents a comparison of wind-induced cladding damage, from a "design" cyclone proposed by Jancauskas, et al. (1994), with current test criteria developed by Mahendran (1995). Wind tunnel data were used to generate the external and net pressure time histories on the roof of a low-rise building during the passage of the "design" cyclone. The peak pressures generated at the windward roof corner for a tributary area representative of a cladding fastener are underestimated by the Australian/New Zealand Wind Actions Standard. The "design" cyclone, with increasing and decreasing wind speeds combined with changes in wind direction, generated increasing then decreasing pressures in a manner similar to that specified in the L-H-L test. However, the L-H-L test underestimated the magnitude and number of large load cycles, but overestimated the number of cycles in the mid ranges. Cladding elements subjected to the L-H-L test showed greater fatigue damage than when experiencing a five hour "design" cyclone containing higher peak pressures. It is evident that the increased fatigue damage was due to the L-H-L test having a large number of load cycles cycling from zero load (R=0) in contrast to that produced during the cyclone.

• 한국강구조학회 논문집
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• 제21권3호
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• pp.289-299
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• 2009

본 연구는 각주형 저층건축물에 작용하는 지점별 풍압을 다점동시측정시스템을 이용하여 건물 폭과 깊이변화에 따른 평균풍압분포 특성에 대한 기초적인 결과를 정리한 것이다. 본 실험에서는 건물의 폭과 깊이를 변화시킨 5개의 각주형 풍압실험모형이 사용되었으며, 풍동실험은 금오공과대학교 소재 토출식 경계층풍동에서 실시하였다. 실험결과는 저층건축물의 건물 폭 및 깊이의 변화에 따른 저층건축물의 평균풍압분포 변화경향을 건축물의 풍상면, 풍측면 및 풍하면 중심으로 특성을 분석하였다. 실험결과를 토대로 저층건축물의 구조골조 설계용 풍하중을 합리적으로 산정하기 위해 필요한 새로운 풍압계수 및 간략한 약산식을 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1482-1489
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• 2007

In this paper, characteristics of infrasound and low-frequency noise emission from large modern wind turbines are experimentally investigated. The sound measurement procedures of IEC 61400-11 and ISO 7196 are utilized to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbines using the stall regulation and the pitch control for the power regulation, respectively. It was found that the G-weighted SPLs of low-frequency noise including infrasound shows positive correlation with the wind speeds, irrespective of methods of power regulation. This highlights the potential complaint of local community against the infrasound and low-frequency noise of wind turbines. The comparison of measured data with the existing hearing thresholds and criteria curves shows that it is highly probable that the low-frequency noise from the 1.5 MW and 660 kW wind turbines in the frequency range over 30 Hz leads to the psychological complaint of ordinary adults, and that the infrasound in the frequency range from 5 Hz to 8 Hz causes the complaint by rattling the house fitting such as doors and windows.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.1080-1088
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• 2014

By combining a wind turbine with an energy storage system (ESS), we are able to attenuate the intermittent wind power characteristic making the power derived from a wind farm dispatchable. This paper evaluates the influence of the phase delay of the low-pass filter in the conventional smoothing power control on the ESS capacity; longer phase delays require a larger ESS capacity. In order to eliminate the effect of the phase delay, we optimize the power dispatch using a zero-phase low-pass filter that results in a non-delayed response in the power dispatch. The proposed power dispatching method significantly minimizes the ESS capacity. In addition, the zero-phase low-pass filter, which is a symmetrical forward-reverse finite impulse response type, is designed simply with a small number of coefficients. Therefore, the proposed dispatching method is not only optimal, but can also be feasibly applied to real wind farms. The efficacy of the proposed dispatching method is verified by integrating a 3 MW wind turbine into the grid using wind data measured on Jeju Island.

• 한국항공운항학회지
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• 제19권4호
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• pp.24-29
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• 2011

Conceptual study of an open-circuit type low-speed wind tunnel for performance test of wind turbine blade and airfoil is conducted. The tunnel is constituted of a settling chamber, a contraction, closed test section, a diffuser, two corners, a cross leg and a fan and motor. For the performance test, the closed test section width of 1.8 m, height of 1.8 m and length of 5.25 m is selected. The contraction ratio is 9 to 1 and maximum speed in the test section is 67 m/sec. Input power in the tunnel is about 238 kW and its energy ratio is 3.6. The wind tunnel designed in present study will be an effective tool in research and development of wind turbine and airfoil.

• 한국환경과학회지
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• 제5권6호
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• pp.713-718
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• 1996

We identified two characteristic turbulent flow cases, weakening and strengthening, which appear at the downwind side. Observations were made two times, Dec. 2-3. 1995 and Feb. 13-14. 1996 at Pusan National University site located downwind side of Kumjeong mountain. Meteorological observation system, tethersonde, was adopted to present observation. In the case of the west wind which blows perpendicular to Sanghak mountain located westward from the site, the wind speed highly increased in exponential with height. Therefore, the low level wind speed was so weak just like Taylor(1988)'s review. While the wind speed was intensified at 200-400m layer when the northwest wind blows from the continental Siberian high. We suppose 기 is because of the strong vertical convergence of flow between the surface inversion layer and the upper one, and also the horizontal convergence along the saddle and valley between the two mountains, Kumjeong and Sanghak-because of Bernoulli's effect. The inversion layer existed at surface-l00m and 500-600m level and the strong wind existed at about 200-400m layer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.307-308
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• 2006

The national goal of wind energy dissemination has to be determined rationally based on technically available wind resource potential. For a reliable and scientific estimation or wind resource potential, a wind map is requisite. This paper presents the national wind map of Korea established by numerical wind simulation. Prediction accuracy of the low-resolution wind map is Improved by nudging QuikSCAT data and is validated by comparing with marine buoy beacon and met-mast measurements. Therefore, quantification of national wind resource potential is now possible and is anticipating to be utilized as a core index for policy and strategy building of wind energy dissemination and technology development.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.820-826
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• 2014

It is well known that energy generated by a wind generator (WG) depends on the wind resources at the installation site. In other words, a WG installed in a high wind speed area can produce more energy than that in a low wind speed area. However, a WG installed at a low wind site can produce a similar amount of energy to that produced by a WG installed at a high wind site if the WG is designed with a rated wind speed corresponding to the mean wind speed of the site. In this paper, we investigated the power curve of a WG suitable for Korea's southwestern coast with a low mean wind speed to achieve a high capacity factor (CF). We collected the power curves of the 11 WGs of the 6 WG manufacturers. The probability density function of the wind speed on Korea's southwestern coast was modeled using the Weibull distribution. The annual energy production by the WG was calculated and then the CFs of all of the WGs were estimated and compared. The results indicated that the WG installed on the Korea's southwestern coast could obtain a CF higher than 40 % if it was designed with the lower rated speed corresponding to the mean wind speed at the installation site.

• International Journal of Aerospace System Engineering
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• 제10권2호
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• pp.1-4
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• 2023

Even though the recent development trend of wind turbine systems has been focused on larger MW Classes, the small-scale wind turbine system has been continuously developed because it has some advantages due to easy personnel establishment and use with low cost and energy saving effect. This work is to propose a specific structural design and analysis procedure for development of a low noise 500W class small wind turbine system which will be applicable to relatively low wind speed region like Korea. The proposed structural feature has a skin-spar-foam sandwich composite structure with the E-glass/Epoxy face sheets and the Urethane foam core for lightness, structural stability, low manufacturing cost and easy manufacturing process. Moreover this type of structure has good behaviors for reduction of vibration and noise. Structural analysis including load cases, stress, deformation, buckling and vibration was performed using the Finite Element Method. In order to evaluate the designed blade structure the structural tests were done, and their test results were compared with the estimated results.

• Wind and Structures
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• 제35권4호
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• pp.255-268
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• 2022

Light-weight or low-damped structures may encounter the unsteady galloping instability that occurs at low reduced wind speeds, where the classical quasi-steady assumption is invalid. Although this unsteady phenomenon has been widely studied for rectangular cross sections with one side perpendicular to the incidence flow, the effect of the mean wind angle of attack has not been paid enough attention yet. With four sectional models of different side ratios and geometric shapes, the presented research focuses on the effect of the wind angle of attack on unsteady galloping instability. In static tests, comparatively strong vortex shedding force was noticed in the middle of the range of flow incidence where the lift coefficient shows a negative slope. In aeroelastic tests with a low Scruton number, the typical unsteady galloping, which is due to an interaction with vortex-induced vibration and results in unrestricted oscillation initiating at the Kármán vortex resonance wind speed, was observed for the wind angles of attack that characterize relatively strong vortex shedding force. In contrast, for the wind angles of attack with relatively weak shedding force, an "atypical" unsteady galloping was found to occur at a reduced wind speed clearly higher than the Kármán-vortex resonance one. These observations are valid for all four wind tunnel models. One of the wind tunnel models (with a bridge deck cross section) was also tested in a turbulent flow with an intensity about 9%, showing only the atypical unsteady galloping. However, the wind angle of attack with the comparatively strong vortex shedding force remains the most unfavorable one with respect to the instability threshold in low Scruton number conditions.