• Interaction and multiscale mechanics
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• 제5권2호
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• pp.91-104
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• 2012

There is relatively little numerical study on the behavior of eccentrically loaded high strength rectangular concrete-filled steel tubular (CFST) slender beam-columns with large depth-to-thickness ratios, which may undergo local and global buckling. This paper presents a multiscale numerical model for simulating the interaction local and global buckling behavior of high strength thin-walled rectangular CFST slender beam-columns under eccentric loading. The effects of progressive local buckling are taken into account in the mesoscale model based on fiber element formulations. Computational algorithms based on the M$\ddot{u}$ller's method are developed to obtain complete load-deflection responses of CFST slender beam-columns at the macroscale level. Performance indices are proposed to quantify the performance of CFST slender beam-columns. The accuracy of the multiscale numerical model is examined by comparisons of computer solutions with existing experimental results. The numerical model is utilized to investigate the effects of concrete compressive strength, depth-to-thickness ratio, loading eccentricity ratio and column slenderness ratio on the performance indices. The multiscale numerical model is shown to be accurate and efficient for predicting the interaction buckling behavior of high strength thin-walled CFST slender beam-columns.

• 한국대기환경학회지
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• 제16권5호
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• pp.511-520
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• 2000

The urban atmosphere is characterized by th difference in surface and atmospheric environment between urban and more natural area. To investigate th climatic effect of land use type and anthropogenic heat of urban on wind field, numerical simulations were carried out under typical summer synoptic condition. The wind model PNU_MCM(Pusan National University Mesoscale Circulation Model) is based on the three-dimensional Boussinesq equations, taking into account the hydrostatic assumption . Since lane-use differs over every subdivision on Pusan the surface energy budget model includes sub0grid parameterization scheme which can calculate the total heat flux over a grid surface composed of different surfaces. The simulated surface wind agrees well with the observed value, and average over 6 days which represent typical summer lan-sea breeze days, August 1998, i.e. negligible gradient winds and almost clear skies. Urbanization makes sea-breeze enhance at day and reduce land-breeze at night. The results show that contribution of land-use type is much larger than that of anthropogenic heat in Pusan.

• 한국항공운항학회지
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• 제14권4호
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• pp.94-100
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• 2006

The purpose of this case study is to determine the possibility of Numerical Forecasting of sea fog at West Sea in spring time. For practical method of analyzing the data collected from 24th to 26th March 2003, Numerical Weather Prediction model MM5(Mesoscale Model Version 5) and synoptic field study using synoptic chart, upper level chart, and sea surface temperature were employed. The results of synoptic field analysis summarized that sea fog at West sea in spring is intensified by the inflow of the warm flow from west or southwest, low sea surface temperature to increase the temperature difference between air and sea surface, and inversion layer to disturb the disperse. It appears that the possibility of sea fog forecasting by MM5, in view of the result that the MM5 output is similar to the synoptic fields analysis.

• 한국해안해양공학회지
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• 제6권3호
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• pp.298-308
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• 1994

북서태평양의 해수순환을 원시방정식 수처모형을 이용하여 재현하여 알라스카 만에서 관측된 해수순환의 경년변화에 대한 설명을 시도하였다. 모형 결과에 의하면 알라스카 gyre의 계절적 위치 변동은 없으며, 관측된 경년변화는 중규모 와류가 역학심도 계산에 영향을 미친 결과로 보인다. 이러한 중규모 와류는 수온 염분 관측, 부표추적 실험, 그리고 인공위성에 의한 해수면 관측에서도 관측되었다.

• 한국지구과학회지
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• 제26권1호
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• pp.66-77
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• 2005

한반도 남서해안에 위치한 흑산도 고층관측이 2003년 6월 1일부터 실시되고 있다. 이러한 흑산도 관측자료에 의한 수치예보개선효과를 보기 위하여 광주의 관측자료와 비교 분석하였다. 분석에는 MM5를 기본으로 제작한 호남지방 고밀도 예측시스템을 이용하였다. 먼저 지표면 마찰과 현열플러스의 차이에 의하여 광주와 흑산도의 바람장과 온도장은 다르게 나타났으며, 광주와 흑산도의 자료를 모두 동화시킨 수치예측 바람장과 기상장이 관측과 제일 잘 일치하였다. 강수면에서 비록 강수량은 과소평가를 하고 있으나, 강수시간과 강수구역은 흑산도자료를 포함하여 자료동화를 시킨 경우 관측과 유사하게 나타났다.

• 한국환경과학회지
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• 제11권4호
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• pp.281-288
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• 2002

This study was carried out for reading the change of local meteorological environment according to dam construction of Nakdong-river using numerical model. The study used PSU/NCAR Mesoscale Model version5(MM5) for inquiring effect of formation of artificial lake after dam construction. The colleague simulated temperature mixing ratio, latent heat flux and sensible heat flux in two cause of existing lake and not. Temperature and mixing ratio in southwest of Andong lake increased because of the air that was warm and moist above the lake moved to southwest due to the northeasterly wind. In the case of existing lake around Andong, latent heat flux increased much in the daytime after sunrise. However, sensible heat flux decreased but it didn't change distinctly in southwest of Andong like the other values.

• 한국지구과학회지
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• 제36권6호
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• pp.567-579
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• 2015

중규모 기상 모델을 이용하여 안개와 같은 미세규모 국지현상을 정확히 재현하는 것은 매우 어려운 실정이다. 특히, 수치모델의 초기 입력 자료의 불확도는 수치모델의 예측 정확도에 결정적인 영향을 미치기 때문에 이를 보완하기 위한 자료동화 과정이 요구되어진다. 본 연구에서는 WRF (Weather Research and Forecasting) 모델을 이용하여 낙동강 지역에서 발생한 여름철 안개사례 재현실험을 대상으로 중규모 기상 모델의 한계를 검증하였다. 중규모 기상 모델에서 초기 및 경계장으로 사용되는 KLAPS (Korea Local Analysis and Prediction System)와 LDAPS (Local Data Assimilation and Prediction System) 분석장 자료를 이용하여 수치모델 모의 정확도 민감도 분석을 수행하였다. 또한 AWS (Automatic Weather System) 자료를 이용한 자료동화(Four-Dimensional Data Assimilation)에 의한 수치모델의 정확도 개선 정도를 평가하였다. 초기 및 경계장 민감도 분석 결과에서 LDAPS 자료를 입력 자료로 사용한 경우가 KLAPS 자료 보다 기온과 이슬점온도, 상대습도에서 높은 정확도를 보였고, 풍속은 더 낮은 수준을 나타내었다. 특히, 상대습도에서 LDAPS의 경우는 RMSE (Root Mean Square Error)가 15.9%, KLAPS는 35.6%의 수준을 보여 그 차이가 매우 크게 나타났다. 또한 자료동화를 통하여 기온, 풍속, 상대습도의 RMSE가 각각 $0.3^{\circ}C$, $0.2ms^{-1}$, 2.2% 수준으로 개선되었다.

• 한국대기환경학회지
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• 제23권6호
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• pp.653-665
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• 2007

Several numerical experiments were carried out to clarify the influence of satellite data assimilation with various spatial resolution on mesoscale meteorological wind and temperature field. Satellite data used in this study is QuikSCAT launched on ADEOS II. QuikSCAT data is reasonable and faithful sea wind data, which have been verified through many observational studies. And numerical model in the study is MM5 developed by NCAR. Difference of wind pattern with and without satellite data assimilation appeared clearly, especially wind speed dramatically reduced on East Sea, when satellite data assimilation worked. And sea breeze is stronger in numerical experiments with RDAPS and satellite data assimilation than that with CDAS and data assimilation. This caused the lower estimated surface temperature in CDAS used cases. Therefore the influence of satellite data assimilation acts differently according to initial data quality. And it is necessary to make attention careful to handle the initial data for numerical simulations.

• 한국대기환경학회지
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• 제20권1호
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• pp.1-15
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• 2004

Sea/land circulation system is a representative mesoscale local circulation system in coastal area. In this study, wind fields around coastal area. Pohang, which is affected by this system was investigated and its detailed characteristic analysis was carried out. The following can be found out from the numerical simulation. Generally, at nighttime mountain winds prevail and land breeze toward the coastal area was well simulated During daytime, valley wind and sea breeze was simulated in detail. Especially, as a result of analyzing the land breeze path, it could be found along the coastline as it flows out through low land coastal area. In order to investigate the accuracy of model results. wind speed, temperature and wind direction of continuous typical sea/land breeze occurrence day was compared with observation data. Analyzing the characteristics of local circulation system was very hard because of horizontally sparse observation data but from the above result, a numerical simulation using RAMS, which satisfies the spatial high resolution, will provide more accurate results.

• 한국환경과학회지
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• 제2권2호
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• pp.103-113
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• 1993

The land and sea breeze over the Pusan coastal area is studied by three dimensional mesoscale numerical model. According to the results of the simulation experiments, both Pusan areas and Kimhae areas, the sea breeze began at 0800LST and the strongest at 1500LST and then at 1800LST. After midnight, the sea breeze changed about the land breeze and become weaker than that of the sea breeze in the daytime. Comparisons between calculations and observations showed that the characteristics of diurnal variation and v-component of the wind velocity relatively is similar to the Pusan areas. On the Kimhae areas, however, observations showed time lag which compared to the results of simulation experiments in the velocity of sea breeze and diurnal variation. From the above results, comparisons between calculations and observations is much more similar to the coastal areas than on the inland area.