• 한국강구조학회 논문집
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• 제17권3호통권76호
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• pp.263-270
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• 2005

본 연구에서는 강풍을 받는 차량의 주행안정성을 증가시키기 위한 일련의 종합적인 대책을 제시하였다. 본 연구는 크게 세가지 부분으로 구성된다. 첫 번째로 차종별 속도제한 및 통행제한 기준을 마련하였다. 두 번째는 방풍대책의 필요여부를 판단할 설치 기준을 작성하는 것으로, 국부적인 지형의 보정을 통한 기상자료의 확률적인 모델을 이용하여 위험도를 판단하는 과정을 제시하였다. 세 번째는 풍속을 저감시킬 수 있는 효과적인 방풍벽을 제안하는 것으로 전산유체해석과 풍동실험을 통하여 풍속감소 효과, 경제성, 시각적 개방성을 고려한 방풍벽을 설계하였다. 아울러 현장실험을 통하여 4가지 방풍벽의 성능에 대한 검증을 하였다.

• 한국대기환경학회지
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• 제23권3호
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• pp.322-331
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• 2007

In this study, we have analyzed $PM_{10}$ concentration measured at Incheon Regional Air Monitoring Network (10 stations) and meteorological data at Incheon Weather Station to investigate factors (i.e. wind direction, wind speed, relative humidity, major meteorological phenomenon, and sea-land breezes existence) influencing $PM_{10}$ concentration in Incheon during 2005. Statistical differences among meteorological factors were assessed by Kruskal-Wallis test or Mann-Whitney U test. The main conditions causing high $PM_{10}$ concentration are summarized below; 1. When westerly wind prevailed (however, $PM_{10}$ decreased when winds were blowing from the east or north). 2. When the winds were calm, owing to accumulation of nearby emissions under stagnant conditions, or when the wind speed is in excess of 6 m/s, which shows the effect of fugitive dust produced by wind erosion. 3. Under the condition of high relative humidity and poor diffusion based on meteorological phenomenon such as fog, mist, and haze. 4. When the Sea-Land breezes existed, which occurred 70 days in Incheon during 2005 and contributed significantly to high $PM_{10}$ concentration in the coastal urban area. In conclusion, we have found that the meteorological factors have influence on $PM_{10}$ concentration in Incheon.

• Wind and Structures
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• 제26권3호
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• pp.147-161
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• 2018

For wind engineering applications downbursts are, presently, almost exclusively modeled, both experimentally and numerically, as transient impinging momentum jets (IJ), even though that model contains none of the physics of real events. As a result, there is no connection between the IJ-simulated downburst wind fields and the conditions of formation of the event. The cooling source (CS) model offers a significant improvement since it incorporates the negative buoyancy forcing and baroclinic vorticity generation that occurs in nature. The present work aims at using large-scale numerical simulation of downburst-producing thunderstorms to develop a simpler model that replicates some of the key physics whilst maintaining the relative simplicity of the IJ model. Using an example of such a simulated event it is found that the non-linear scaling of the velocity field, based on the peak potential temperature (and, hence, density) perturbation forcing immediately beneath the storm cloud, produces results for the radial location of the peak radial outflow wind speeds near the ground, the magnitude of that peak and the time at which the peak occurs that match well (typically within 5%) of those produced from a simple axi-symmetric constant-density dense source simulation. The evolution of the downdraft column within the simulated thunderstorm is significantly more complex than in any axi-symmetric model, with a sequence of downdraft winds that strengthen then weaken within a much longer period (>17 minutes) of consistently downwards winds over almost all heights up to at least 2,500 m.

• 한국대기환경학회지
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• 제15권4호
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• pp.441-455
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• 1999

Meteorological characteristics of three high-ozone episodes in the Greater Seoul Area, selected on the basis of morning-average wind direction and speed for the 1990~1997 period, were investigated. Three high-ozone episodes thus selected were seven days of July 3~9, 1992, nine days of July 21~29, 1994, and three days of August 22~24, 1994. Along with surface meteorological data from the Seoul Weather Station, surface and 850-hPa wind fields over the Northest Asia around the Korean Peninsula were used for the analysis. In the July 1992 episode, westerly winds were most frequent as a result of the influence of a high-pressure system in the west behind the trough. In contrast, in the July 1994 episode, easterly winds were most frequent due to the effect of a typhoon moving north from the south of Japan. Despite different prevailing wind directions in the two episodes, the peak ozone concentration of each episode always occurred when a sea-land breeze developed in association with weak synoptic forcing. The August 1994 episode, selected as being representative of calm conditions, was another typical example in which peak ozone concentration rose to 322 ppb under the well-developed sea-land breeze. All three high-ozone episodes were terminated by precipitation, and subsequent rises in ozone concentrations were also suppressed by a series of precipitation afterwards. In particular, two heavy rainfalls were the main reason why the August 1994 episode, with the highest and second-highest ozone concentrations during the 1990~1997 period, lasted for only a few days.

• 한국환경과학회지
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• 제11권1호
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• pp.41-56
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• 2002

In order to estimate the quantitative roles of the tide induced residual currents, density currents and wind driven currents on the residual currents in Kwangynag Bay Korea, numerical experiments with a diagnostic multi-level model were carried out. Density currents were calculated from the temperature and salinity data observed in January, May, August and November 1998. Anti-clockwise circulations are formed at the western inner part of the bay, the location from the east of Myodo Is. to the south of POSCO Co. and the place between Yeosu peninsula and Namhae Is. from the calculation results of the tide induced residual currents. Velocities of the density currents are less than 3cm/s at the western inner part of the bay and about 5cm/s at the southern entrance of the bay. Density currents get strong in summer and weak in autumn. Wind driven currents at the surface layer flow in the directions of the given winds which are the daily mean winds when the temperature and salinity observations are carried out. In the middle and lower layers, however the wind driven currents flow in the opposite direction to the surface currents as supplementary currents. The surface wind driven currents are greater than the tide induced residual currents or the density currents. The calculated residual currents including the tide induced residual currents, density currents and wind driven currents agree with the results of the current observations approximately. In the Bay, the wind driven currents affect on the residual currents greatestly and tide induced residual currents and density currents do in the second place and the third place.

• 대한기계학회논문집A
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• 제38권7호
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• pp.699-709
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• 2014

본 논문에서는 단일윤축 탈선이론을 적용하여 측풍 조건에서 주행 중인 철도차량의 탈선을 예측하는 방법을 제시하였다. 기존 연구에서는 측풍에 의한 탈선은 모두 전복탈선이라고 가정하여 탈선 예측 이론을 개발하였다. 그러나 이러한 가정은 특수한 주행조건하에서 차륜 타고오름 탈선의 가능성을 무시하고 있다. 또 기존의 측풍 탈선 이론은 주행 중 발생하는 차륜-궤도 사이의 마찰력, 동적상호작용과 같은 주행조건이 탈선에 미치는 영향을 고려할 수 없었다. 본 논문의 방법은 차륜-궤도 사이의 동적 영향, 횡가속도 및 켄트 영향, 측풍 영향 등을 동시에 고려할 수 있었다. 본 이론의 결과를 기존 이론 및 시뮬레이션 결과와 비교하여 타당성을 검증하였다.

• Journal of the korean society of oceanography
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• 제39권1호
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• pp.72-95
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• 2004

The Yellow Sea is characterized by relatively shallow water depth, varying range of tidal action and very complex coastal geometry such as islands, bays, peninsulas, tidal flats, shoals etc. The dynamic system is controlled by tides, regional winds, river discharge, and interaction with the Kuroshio. The circulation, water mass properties and their variability in the Yellow Sea are very complicated and still far from clear understanding. In this study, an effort to improve our understanding the dynamic feature of the Yellow Sea system was conducted using numerical simulation with the ROMS model, applying climatologic forcing such as winds, heat flux and fresh water precipitation. The inter-annual variability of general circulation and thermohaline structure throughout the year has been obtained, which has been compared with observational data sets. The simulated horizontal distribution and vertical cross-sectional structures of temperature and salinity show a good agreement with the observational data indicating significantly the water masses such as Yellow Sea Warm Water, Yellow Sea Bottom Cold Water, Changjiang River Diluted Water and other sporadically observed coastal waters around the Yellow Sea. The tidal effects on circulation and dynamic features such as coastal tidal fronts and coastal mixing are predominant in the Yellow Sea. Hence the tidal effects on those dynamic features are dealt in the accompanying paper (Kim et at., 2004). The ROMS model adopts curvilinear grid with horizontal resolution of 35 km and 20 vertical grid spacing confirming to relatively realistic bottom topography. The model was initialized with the LEVITUS climatologic data and forced by the monthly mean air-sea fluxes of momentum, heat and fresh water derived from COADS. On the open boundaries, climatological temperature and salinity are nudged every 20 days for data assimilation to stabilize the modeling implementation. This study demonstrates a Yellow Sea version of Atlantic Basin experiment conducted by Haidvogel et al. (2000) experiment that the ROMS simulates the dynamic variability of temperature, salinity, and velocity fields in the ocean. However the present study has been improved to deal with the large river system, open boundary nudging process and further with combination of the tidal forcing that is a significant feature in the Yellow Sea.

• 해양환경안전학회지
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• 제15권1호
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• pp.49-55
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• 2009

우리나라는 매년 최소 3${\sim}$4개 정도의 태풍의 영향을 받고 있으며, 이러한 태풍은 강한 바람과 많은 비를 동반하여 막대한 재산피해와 인명피해를 가져왔다. 특히, 태풍 매미는 기록적인 강풍과 높은 파도를 동반하여 피항지에 묘박중인 선박들과 부두에 계류중인 선박들이 침몰, 좌초, 충돌하는 등 많은 해양사고를 유발시켰다. 태풍의 내습이 예상되면 선박들은 태풍의 예상 진로에서 멀리 벗어나거나 안전한 피항지를 선택하여 투묘를 실시하고 있다. 하지만, 투묘에 대한 사항이나 투묘 후 선박의 안전에 대한 판단은 운항자의 경험에 의존하고 있는 실정이다. 따라서, 본 논문에서는 실습선 한바다호를 대상으로 선체에 작용하는 외력과 외력에 대한 대항력을 상호 비교 분석함으로써 선박의 묘박 안전성을 정량적으로 평가하였고, 이를 바탕으로 주묘 한계풍속, 선박에서의 안전대책, 단계별 조치사항 등에 대한 묘박 매뉴얼을 개발하였다.

• 해양환경안전학회지
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• 제19권6호
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• pp.561-569
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• 2013

본 연구에서는 우리나라 연안의 2003~2009년 해수면자료로 조위편차를 산출하고, 일평균조위편차의 시공간적 변동을 EOF 분석, 해면기압과 바람이 조위편차 변동에 얼마나 영향을 미치는지를 상관성 분석을 통해 알아보았다. 일평균조위편차는 전체 변동량의 68 %(제1모드)가 동시승강하였고, 전체 변동량의 21 %(제2모드)는 서해안이 상승할 때 남해안과 동해안이 하강하는 교차승강을 하였다. 해역별로 조위편차에 영향을 주는 주요 요인을 보면, 서해안은 남-북 방향의 바람 성분이었고, 남해안은 동해안으로 갈수록 해면기압의 영향이 우세하였다.

• Wind and Structures
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• 제25권1호
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• pp.79-100
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• 2017

The use of wind energy resources is developing rapidly in recent decades. There is an increasing number of wind farms in high wind-velocity areas such as the Pacific Rim regions. Wind turbine towers are vulnerable to tropical cyclones and tower failures have been reported in an increasing number in these regions. Existing post-disaster failure case studies were mostly performed through forensic investigations and there are few numerical studies that address the collapse mode simulation of wind turbine towers under strong wind loads. In this paper, the wind-induced failure analysis of a conventional 65 m hub high 1.5-MW wind turbine was carried out by means of nonlinear response time-history analyses in a detailed finite element model of the structure. The wind loading was generated based on the wind field parameters adapted from the cyclone boundary layer flow. The analysis results indicate that this particular tower fails due to the formation of a full-section plastic hinge at locations that are consistent with those reported from field investigations, which suggests the validity of the proposed numerical analysis in the assessment of the performance of wind-farms under cyclonic winds. Furthermore, the numerical simulation allows to distinguish different failure stages before the dynamic collapse occurs in the proposed wind turbine tower, opening the door to future research on the control of these intermediate collapse phases.