• 대한토목학회논문집
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• 제29권3A호
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• pp.209-216
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• 2009

풍하중이 지배적인 구조물의 경우에 정확한 설계풍속의 산정은 구조적 안정성뿐만 아니라 경제성까지도 좌우하게 된다. 본 연구에서는 광양대교 현장에 설치된 관측탑에서 약 1년간 측정한 풍속을 사용하여 풍환경을 분석하였고, MCP(Measure-Correlate-Predict) 방법을 적용하여 관측치로부터 장기 풍속을 추정하였다. 그 결과를 보면, 광양만은 바다이지만 개활지에 가까운 풍속 특성을 나타내고 있으며, 조도지수는 고도에 따라 달라지는 것으로 나타났다. 아울러 풍향에 따라 난류강도와 조도지수가 상당히 차이나는 것으로 나타났다. MCP 방법으로 추정한 200년빈도 설계풍속은 초기설계치보다 20 m/s이상 낮았으며, 실측된 풍속과 거스트계수를 고려한 설계풍하중은 초기설계치의 36%밖에 안되는 것으로 나타났다. 이를 볼 때 국부적인 지형의 영향으로 추정한 교량 현장의 풍환경과 직접 측정한 풍환경은 차이가 나므로, 경제적이고 안전한 설계를 위해서는 단기간이라도 현장 풍환경 관측이 필요하다고 판단된다.

• 한국대기환경학회지
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• 제19권3호
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• pp.249-261
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• 2003

A three-dimensional mesoscale atmospheric dispersion modeling system consisting of the Lagrangian particle dispersion model (LPDM) and the meteorological mesoscale model (MM5) was employed to simulate the transport and dispersion of non-reactive pollutant during the nuclear spill event occurred from Sep. 31 to Oct. 3, 1999 in Tokaimura city, Japan. For the comparative analysis of numerical experiment, two more sets of foreign mesoscale modeling system; NCEP (National Centers for Environmental Prediction) and DWD (Deutscher Wetter Dienst) were also applied to address the applicability of air pollution dispersion predictions. We noticed that the simulated results of horizontal wind direction and wind velocity from three meteorological modeling showed remarkably different spatial variations, mainly due to the different horizontal resolutions. How-ever, the dispersion process by LPDM was well characterized by meteorological wind fields, and the time-dependent dilution factors ($\chi$/Q) were found to be qualitatively simulated in accordance with each mesocale meteorogical wind field, suggesting that LPDM has the potential for the use of the real time control at optimization of the urban air pollution provided detailed meteorological wind fields. This paper mainly pertains to the mesoscale modeling approaches, but the results imply that the resolution of meteorological model and the implementation of the relevant scale of air quality model lead to better prediction capabilities in local or urban scale air pollution modeling.

• Wind and Structures
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• 제7권6호
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• pp.421-447
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• 2004

This paper presents a time domain approach for predicting buffeting response of long suspension bridges under skew winds. The buffeting forces on an oblique strip of the bridge deck in the mean wind direction are derived in terms of aerodynamic coefficients measured under skew winds and equivalent fluctuating wind velocities with aerodynamic impulse functions included. The time histories of equivalent fluctuating wind velocities and then buffeting forces along the bridge deck are simulated using the spectral representation method based on the Gaussian distribution assumption. The self-excited forces on an oblique strip of the bridge deck are represented by the convolution integrals involving aerodynamic impulse functions and structural motions. The aerodynamic impulse functions of self-excited forces are derived from experimentally measured flutter derivatives under skew winds using rational function approximations. The governing equation of motion of a long suspension bridge under skew winds is established using the finite element method and solved using the Newmark numerical method. The proposed time domain approach is finally applied to the Tsing Ma suspension bridge in Hong Kong. The computed buffeting responses of the bridge under skew winds during Typhoon Sam are compared with those obtained from the frequency domain approach and the field measurement. The comparisons are found satisfactory for the bridge response in the main span.

• 전기의세계
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• 제22권3호
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• pp.63-71
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• 1973

When ions move in the air under an electric field, momentum is transferred from ions to neighboring particles. The wind is raised therefore, if the ion-flow is dominant in one direction. Using this mechanism, authors developed a fan which has no moving parts, and named it EHD AIR MOVER. This paper describes its theory with experimental results. Air velocity of 450ft/min is obtained by the ion current of 5*10$\^$-6/A/cm$\^$2/. Comparison of the theoretical calculation with the experimental data shows satisfactory agreement.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.511-520
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• 2020

지구온난화로 인해 하절기 폭염현상과 열대야가 강해짐에 따라, 도시공원 등 녹지공간의 열환경 개선에 대한 연구가 활발히 진행 중이다. 하지만, 녹지의 식재패턴과 바람의 세기로 인해 변화하는 도시 열환경 개선 연구는 아직까지 미흡한 실정이다. 본 연구는 공공 휴게 녹지공간의 온도분석 및 온도의 변화요인을 파악하는데 목적이 있다. 대상지로는 전남대학교 민주마루 앞 광장을 설정하였다. 대상지의 피복상태, 식재형태를 조사 후, 온도, 습도, 풍향, 풍속 등을 측정하여 요인들을 분석하였다. 측정기준은 기상청 기준 오후 2시에 전운량 30% 이하, 습도 90% 이하, 온도는 최고온도 30℃ 이상인 날로 지정하였다. 온도 실측은 크게 1차 실측과 2차 실측으로 구분하여 측정하였다. 1차 실험은 2018년 6월 1일부터 6월 21일까지 30도를 기준일로 6일간, 2차 실험은 2018년 7월 27일부터 8월 1일까지 35도를 기준으로 3일간 측정을 실시하였다. 온도분포에 가장 큰 영향을 미치는 요인은 증발산과 바람에 의한 열 이동으로 판단된다. 온도변화요인으로는 피복유형, 풍속/풍향, 식재유형 등이 있었다. 피복유형에서 목본 식재지는 저온역으로, 초지와 아스팔트 포장은 고온역으로 구분되었다. 풍속/풍향에서는 3.5m/s 이상의 바람이 불어올 때 남풍에서 1.2도, 서풍에서 0.7도, 북풍에서 0.4도, 동풍에서 0.5도씩 순간온도가 저감되었다. 식재유형에서는 녹지량이 많고, 바람의 영향을 많이 받는 형태일수록 온도가 저감되었다. 온도변화요인을 알아보기 위해 등온선을 작성하여, 풍향과 수목식재 위치 관계를 파악하였다.

• Wind and Structures
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• 제24권2호
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• pp.95-118
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• 2017

The present study revealed comparison the pressure distribution on the surfaces of regular cross plan shaped building with angular cross plan shaped building which is being transformed from basic cross plan shaped building through the variation of internal angles between limbs by $15^{\circ}$ for various wind incidence angle from $0^{\circ}$ to $180^{\circ}$ at an interval of $30^{\circ}$. In order to maintain the area same the limbs sizes are slightly increased accordingly. Numerical analysis has been carried out to generate similar nature of flow condition as per IS: 875 (Part -III):1987 (a mean wind velocity of 10 m/s) by using computational fluid dynamics (CFD) with help of ANSYS CFX ($k-{\varepsilon}$ model). The variation of mean pressure coefficients, pressure distribution over the surface, flow pattern and force coefficient are evaluated for each cases and represented graphically to understand extent of nonconformities due to such angular modifications in plan. Finally regular cross shaped building results are compared with wind tunnel results obtained from similar '+' shaped building study with similar flow condition. Reduction in along wind force coefficients for angular crossed shaped building, observed for various skew angles leads to develop lesser along wind force on building compared to regular crossed shaped building and square plan shaped building. Interference effect within the internal faces are observed in particular faces of building for both cases, considerably. Significant deviation is noticed in wind induced responses for angular cross building compared to regular cross shaped building for different direction wind flow.

• Wind and Structures
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• 제35권5호
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• pp.309-322
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• 2022

Due to the complex terrain around high-speed railways, the windbreaks were established along different landforms, resulting in irregular windbreak transition regions between different subgrade infrastructures (flat ground, cutting, embankment, etc). In this paper, the effect of a windbreak transition on the wind flow around railways subjected to crosswinds was studied. Wind tunnel testing was conducted to study the wind speed change around a windbreak transition on flat ground with a uniform wind speed inflow, and the collected data were used to validate a numerical simulation based on a detached eddy simulation method. The validated numerical method was then used to investigate the effect of the windbreak transition from the flat ground to cutting (the "cutting" is a railway subgrade type formed by digging down from the original ground) for three different wind incidence angles of 90°, 75°, and 105°. The deterioration mechanism of the flow fields and the reasons behind the occurrence of the peak wind velocities were explained in detail. The results showed that for the windbreak transition on flat ground, the impact was small. For the transition from the flat ground to the cutting, the influence was relatively large. The significant increase in the wind speeds was due to the right-angle structure of the windbreak transition, which resulted in sudden changes of the wind velocity as well as the direction. In addition, the height mismatch in the transition region worsened the protective effect of a typical windbreak.

• Smart Structures and Systems
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• 제14권3호
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• pp.419-444
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• 2014

Within this paper a new approach for early damage detection in rotor blades of wind energy converters is presented, which is shown to have a more sensitive reaction to damage than eigenfrequency-based methods. The new approach is based on the extension of Gasch's proportionality method, according to which maximum oscillation velocity and maximum stress are proportional by a factor, which describes the dynamic behavior of the structure. A change in the proportionality factor can be used as damage indicator. In addition, a novel deflection sensor was developed, which was specifically designed for use in wind turbine rotor blades. This deflection sensor was used during the experimental tests conducted for the measurement of the blade deflection. The method was applied on numerical models for different damage cases and damage extents. Additionally, the method and the sensing concept were applied on a real 50.8 m blade during a fatigue test in the edgewise direction. During the test, a damage of 1.5 m length was induced on the upper trailing edge bondline. Both the initial damage and the increase of its length were successfully detected by the decrease of the proportionality factor. This decrease coincided significantly with the decrease of the factor calculated from the numerical analyses.

• 한국환경과학회지
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• 제22권8호
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• pp.1029-1041
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• 2013

In this study, eight episode days of high-concentration $PM_{10}$ occurrences in the Gimhae region between 2006 and 2011 were analyzed. Most of them appeared in winter and the highest concentration was observed around 12 LST. Furthermore, the wind direction, wind velocity, and temperature elements were compared with observed values to verify the WRF numerical simulation results used in this study, and they simulated well in accordance with the trend of the observed values. The wind was generally weak in the high-concentration episode days that were chosen through surface weather chart and the numerical simulation results for wind field, and the air pollutants were congested due to the effects of the resulting local winds, thereby causing a high concentration of air pollutants. Furthermore, the HYSPLIT model was performed with the WRF numerical simulation results as input data. As a result, they originated from China and flowed into Gimhae in all eight days, and the lowest concentration appeared on the days when recirculation occurred.

• 센서학회지
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• 제25권2호
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• pp.86-90
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• 2016

A 3D ultrasonic anemometer measures the direction and velocity of wind in a 3D space. The 2D ultrasonic anemometers developed by different manufacturers do not differ significantly in terms of their form or structure. The 3D ultrasonic anemometers, on the other hand, have more diverse forms than their 2D counterparts depending on the measurement algorithms and methods. Designing and reviewing the structure at the initial stage and defining its performance objectives are time-consuming processes. The process can be made cost-effective and time-saving if the validity is tested by model design and structural interpretation, and the structure is designed to withstand high wind velocities. This study presents the results of a 3D ultrasonic anemometer on real sample data by using a 3D modeling program, CATIA, for ultrasonic anemometer modeling.