• Wind and Structures
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• 제22권1호
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• pp.65-87
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• 2016

The wind velocity profile over the height of a structure in high intensity wind (HIW) events, such as downbursts, differs from that associated with atmospheric boundary layer (ABL) winds. Current design codes for lattice transmission structures contain only limited advice on the treatment of HIW effects, and structural design is carried out using wind load profiles and response factors derived for ABL winds. The present study assesses the load-deformation curve (capacity curve) of a transmission tower under modeled downburst wind loading, and compares it with that obtained for an ABL wind loading profile. The analysis considers nonlinear inelastic response under simulated downburst wind fields. The capacity curve is represented using the relationship between the base shear and the maximum tip displacement. The results indicate that the capacity curve remains relatively consistent between different downburst scenarios and an ABL loading profile. The use of the capacity curve avoids the difficulty associated with defining a reference wind speed and corresponding wind profile that are adequate and applicable for downburst and ABL winds, thereby allowing a direct comparison of response under synoptic and downburst events. Uncertainty propagation analysis is carried out to evaluate the tower capacity by considering the uncertainty in material properties and geometric variables. The results indicated the coefficient of variation of the tower capacity is small compared to those associated with extreme wind speeds.

• 한국환경과학회지
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• 제13권4호
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• pp.367-376
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• 2004

In urban area, thermal pollution associated with heat island phenomena is generally regarded to make urban life uncomfortable. To overcome this urban thermal pollution problem, urban planning with consideration of urban climate, represented by the concept of urban ventilation lane, is widely practiced in many countries. In this study, the prevailing wind ventilation lane of a local winds in Daegu during the warm climate season was investigated by using surface wind data and RAMS(Reasonal Atmospheric Model System) simulation. The domain of interest is the vicinity of Daegu metropolitan city(about 900 $km^{2})$ and its horizontal scale is about 30km. The simulations were conducted under the synoptic condition of late spring with the weak gradient wind and mostly clear sky. From the numerical simulations, the following two major conclusions were obtained: (1)The major wind passages of the local circulation wind generated by radiative cooling over the mountains(Mt. Palgong and Mt. Ap) are found. The winds blow down along the valley axis over the eastern part of the Daegu area as a gravity flow during nighttime. (2)After that time, the winds blow toward the western part of Daegu through the city center. As the result, the higher temperature region appears over the western part of Daegu metropolitan area.

• Wind and Structures
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• 제31권5호
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• pp.445-457
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• 2020

The buffeting response is a vital consideration for long-span bridges in typhoon-prone areas. In the conventional analysis, the turbulence and structural vibrations are assumed as stationary processes, which are, however, inconsistent with the non-stationary features observed in typhoon winds. This poses a question on how the stationary assumption would affect the evaluation of buffeting responses under non-stationary wind actions in nature. To figure out this problem, this paper presents a comparative study on buffeting responses of a long-span cable-stayed bridge based on stationary and non-stationary perspectives. The stationary and non-stationary buffeting analysis frameworks are firstly reviewed. Then, a modal analysis of the example bridge, Sutong Cable-stayed Bridge (SCB), is conducted, and stationary and non-stationary spectral models are derived based on measured typhoon winds. On this condition, the buffeting responses of SCB are finally analyzed by following stationary and non-stationary approaches. Although the stationary results are almost identical with the non-stationary results in the mean sense, the root-mean-square value of buffeting responses are underestimated by the stationary assumption as the time-varying features existing in the spectra of turbulence are neglected. The analytical results highlights a transition from stationarity to non-stationarity in the buffeting analysis of long-span bridges.

• Wind and Structures
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• 제15권2호
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• pp.111-129
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• 2012

Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by sypnoptic events. Wind effects due to other phenomena, such as thunderstorm downbursts, are simply neglected. In this paper, results of recent and ongoing research on this topic in Brazil are presented. The model of the three-dimensional wind velocity field originated from a downburst in a thunderstorm (TS), proposed by Ponte and Riera for engineering applications, is first described. This model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters are related to meteorological variables, which are susceptible of statistical assessment. An application of the model in the simulation of the wind climate in a region sujected to both EPS and TS winds is discussed next. It is shown that, once the relevant meteorological variables are known, the simulation of the wind excitation for purposes of design of transmission lines, long-span crossings and similar structures is feasible. Complementing the theoretical studies, wind velocity records during a recent TS event in southern Brazil are presented and preliminary conclusions on the validity of the proposed models discussed.

• Wind and Structures
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• 제10권5호
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• pp.481-494
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• 2007

Downbursts are transient phenomena that produce wind profiles that are distinctly different from synoptic boundary layers. Wind field data from Computational Fluid Dynamics (CFD) simulations of isolated downburst-like impinging jets, are used to investigate structural loads of tall buildings due to these high intensity winds. The base shear forces and base moments of tall buildings of heights between 120 and 250 m produced by downburst winds of various scales are compared with the forces from the equivalent boundary layer gust winds, with matched 10-metre wind velocity. The wind profiles are mainly functions of the size of the downburst and the radial distance from the centre of the storm. Wind forces due to various downburst profiles are investigated by placing the building at different locations relative to the storm center as well as varying the size of the downburst. Overall it is found that downbursts larger than approx. 2,000 m in diameter might produce governing design wind loads above those from corresponding boundary layer winds for tall buildings.

• Wind and Structures
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• 제24권6호
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• pp.565-578
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• 2017

The meteorological model WRF is used to investigate the wind circulation in Valle Camonica, Italy, an alpine valley that includes a large subalpine lake. The aim was to obtain the information necessary to evaluate the wind potential of this area and, from a methodological point of view, to suggest how numerical modeling can be used to locate the most interesting spots for wind exploitation. Two simulations are carried out in order to analyze typical scenarios occurring in the valley. In the first one, the diurnal cycle of thermally-induced winds generated by the heating-cooling of the mountain range encircling the valley is analyzed. The results show that the mountain slopes strongly affect the low-level winds during both daytime and nighttime, and that the correct setting of the lake temperature improves the quality of the meteorological fields provided by WRF significantly. The second simulation deals with an event of strong downslope winds caused by the passage of a cold front. Comparisons between simulated and measured wind speed, direction and air temperature are also shown.

• 한국컴퓨터그래픽스학회논문지
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• 제27권3호
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• pp.43-53
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• 2021

본 논문은 자동차 핸들과 가속 페달로부터의 온라인 사용자 입력에 따라 Virtual Reality (VR) 환경에서 인공적인 바람을 생성하는 상호작용형 윈드 시스템을 제안한다. 제안된 시스템은 사용자가 레이싱 자동차 VR 응용 콘텐츠에서 세 방향으로부터 불어오는 바람으로부터 촉감을 느끼도록 하기 위해 머리장착형 디스플레이(Head-Mounted Display: HMD)와 세개의 선풍기로 구성된다. VR 멀미를 개선하는 것에 대한 바람의 효과성을 평가하기 위해, 본 논문은 멀미에 대한 가장 기본적인 척도 중의 하나인 SSQ (simulator sickness questionnaire)를 도입한다. 13명의 피험자들을 대상으로 바람이 있는 경우와 그 다음 그렇지 않은 경우 또는 그 역으로 레이싱 자동차 콘텐츠에 대한 실험을 수행하였다. 실험 결과는 인공적인 바람을 사용하는 경우 긍정적인 사용자 경험을 제공하면서 명확하게 멀미를 개선하는 것을 보여주었다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.621-626
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• 2002

A satellite scatterometer is a microwave radar sensor used to measure the backscattering at a sea surface. This instrument transmits radar pulses to the sea surface and measure the radar energy reflected back towards the source. Changes in wind velocity make sea surface roughness change and then affect on backscattered power. This gives us information of sea surface wind speed. Directions of wind vectors are acquired by multiple, collocated, and nearly simultaneous measurements. It should be noted that the scatterometer observes not the wind directly but the wind stress vector relative to the surface current. This suggests the possibility that the satellite scatterometer winds can include the effect of the surface current. This study shows the evidence that scatterometer measure surface wind stress, not surface winds and presents the velocity structure of oceanic warm and cold eddies.

• 한국대기환경학회지
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• 제19권1호
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• pp.13-23
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• 2003

A local wind model and a three dimensional local environmental model including advection, diffusion, deposition. and photochemical reactions were performed at Gwangyang Bay, Korea, to predict air flow and air pollutants concentrations. A large grid was used, and nesting method was employed for small grid calculation. From the meterological module simulation, we were able to reproduce local wind characteristics such as sea/land winds and mountain/valley winds simulation at Gwangyang Bay. In addition, the concentration module showed high concentration regions at Yosu industrial complex, Gwangyang steel company. and Container anchor. It was also seen that air pollutants were dispersed by sea/land winds. A comparison between the measurement and the prediction of sulfur dioxide and nitric oxide, which are relatively low-reacted pollutants, was performed. However, the measured nitrogen dioxide and ozone concentrations were higher than the simulated ones. Particularly, ozone concentration between 8 a..m. and 8 p.m. agreed well, but the measured ozone during the rest of time were generally higher.

• 천문학회지
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• 제29권spc1호
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• pp.253-254
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• 1996

To understand the dynamical structures of stellar wind bubble, one and two-dimensional calculations has been performed. Using FCT Code with cooling effects and assuming constant mass loss rate and ambient medium density, we could divide stellar winds into the regime of slow and fast winds. The slow wind driven bubble shows initially radiative and becomes partially radiative bubble in which shocked stellar wind zone is still adiabatic. In contrast., the fast wind driven bubble shows initially fully adiabatic and becomes adiabatic bubbles with radiative outer shell. We also determine analytically the onset of thin-shell formation time in case of fast wind driven bubble with power-law energy injection and ambient density structure. We solve the line transfer problem with numerical results in order to calculate line profile of [OIII] forbidden line.