• 제목/요약/키워드: Mesoscale

검색결과 292건 처리시간 0.028초

Thermal creep effects of aluminum alloy cladding on the irradiation-induced mechanical behavior in U-10Mo/Al monolithic fuel plates

  • Jian, Xiaobin;Ding, Shurong
    • Nuclear Engineering and Technology
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    • 제52권4호
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    • pp.802-810
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    • 2020
  • Three-dimensional finite element simulations are implemented for the in-pile thermo-mechanical behavior in U-Mo/Al monolithic fuel plates with different thermal creep rates of cladding involved. The numerical results indicate that the thickness increment of fuel foil rises with the thermal creep coefficient of cladding. The maximum Mises stress of cladding is reduced by ~85% from 344 MPa on the 98.0th day when the creep coefficient of cladding increases from 0.01 to 10.0, due to its equivalent thermal creep strain enlarged by 3.5 times. When the thermal creep coefficient of Aluminum cladding increases from 0 to 1.0, the maximum mesoscale stress of fuel foil varies slightly. At the same time, the peak mesoscale normal stress of fuel foil can reach 51 MPa on the 98.0th day for the thermal creep coefficient of 10, which increases by 60.3% of that with the thermal creep un-occurred in the cladding. The maximum through-thickness creep strain components of fuel foil differ slightly for different thermal creep coefficients of cladding. The dangerous region of fuel foil becomes much closer to the heavily irradiated side when the creep coefficient of cladding becomes 10.0. The creep performance of Aluminum cladding should be optimized for the integrity of monolithic fuel plates.

Development of the Korea Ocean Prediction System

  • Suk, Moon-Sik;Chang, Kyung-Il;Nam, Soo-Yong;Park, Sung-Hyea
    • Ocean and Polar Research
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    • 제23권2호
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    • pp.181-188
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    • 2001
  • We describe here the Korea ocean prediction system that closely resembles operational numerical weather prediction systems. This prediction system will be served for real-time forecasts. The core of the system is a three-dimensional primitive equation numerical circulation model, based on ${\sigma}$-coordinate. Remotely sensed multi-channel sea surface temperature (MCSST) is imposed at the surface. Residual subsurface temperature is assimilated through the relationship between vertical temperature structure function and residual of sea surface height (RSSH) using an optimal interpolation scheme. A unified grid system, named as [K-E-Y], that covers the entire seas around Korea is used. We present and compare hindcasting results during 1990-1999 from a model forced by MCSST without incorporating RSSH data assimilation and the one with both MCSST and RSSH assimilated. The data assimilation is applied only in the East Sea, hence the comparison focuses principally on the mesoscale features prevalent in the East Sea. It is shown that the model with the data assimilation exhibits considerable skill in simulating both the permanent and transient mesoscale features in the East Sea.

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낙동강 하천 토지이용 변화에 따른 미세규모 기상 요소의 변동에 관한 수치 연구 (Numerical Study on the Changes in Microscopic Meteorological Elements due to Land Use Variations in the Nakdong River Basin)

  • 김은지;이순환
    • 한국환경과학회지
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    • 제25권12호
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    • pp.1597-1611
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    • 2016
  • A numerical assessment using mesoscale-CFD (computational fluid dynamics) coupled A2C (atmosphere to CFD) model was carried out to analyze the variation of microscopic air flow pattern due to the construction of the Chilgok barrage in the Nakdong River. Scenarios with air flow patterns were classified into pre- and post-construction. The increased width of the river due to the construction of the Chilgok barrage induced obvious changes in moisture and the thermal environment around the river. However, air temperature variation was restricted within an area along the windward side in the numerical assessment. The impact of barrage construction on air temperature tends to be stronger during the nighttime than the daytime. It also stronger during the winter than the summer. In the simulation, the convergence of mesoscale wind is more pronounced after barrage construction than before. This is caused by the change of heat flux pattern induced by the widening of the river. Although this work is a case study with restricted atmospheric stability conditions that has several limitations in the numerical simulations, the impacts of the land-use changes brought about by the construction of the barrage in the river acceptable.

Mesoscale computational simulation of the mechanical response of reinforced concrete members

  • Wang, Licheng;Bao, Jiuwen
    • Computers and Concrete
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    • 제15권2호
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    • pp.305-319
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    • 2015
  • On mesoscopic level, concrete can be treated as a three-phase composite material consisting of mortar, aggregates and interfacial transition zone (ITZ) between mortar and aggregate. A lot of research has confirmed that ITZ plays a crucial role in the mechanical fracture process of concrete. The aim of the present study is to propose a numerical method on mesoscale to analyze the failure mechanism of reinforced concrete (RC) structures under mechanical loading, and then it will help precisely predict the damage or the cracking initiation and propagation of concrete. Concrete is meshed by means of the Rigid Body Spring Model (RBSM) concept, while the reinforcing steel bars are modeled as beam-type elements. Two kinds of RC members, i.e. subjected to uniaxial tension and beams under bending, the fracture process of concrete and the distribution of cracks, as well as the load-deflection relationships are investigated and compared with the available test results. It is found that the numerical results are in good agreement with the experimental observations, indicating that the model can successfully simulate the failure process of the RC members.

수치모델에서 레이더 자료동화가 강수 예측에 미치는 영향 (The Effect of Radar Data Assimilation in Numerical Models on Precipitation Forecasting)

  • 이지원;민기홍
    • 대기
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    • 제33권5호
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    • pp.457-475
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    • 2023
  • Accurately predicting localized heavy rainfall is challenging without high-resolution mesoscale cloud information in the numerical model's initial field, as precipitation intensity and amount vary significantly across regions. In the Korean Peninsula, the radar observation network covers the entire country, providing high-resolution data on hydrometeors which is suitable for data assimilation (DA). During the pre-processing stage, radar reflectivity is classified into hydrometeors (e.g., rain, snow, graupel) using the background temperature field. The mixing ratio of each hydrometeor is converted and inputted into a numerical model. Moreover, assimilating saturated water vapor mixing ratio and decomposing radar radial velocity into a three-dimensional wind vector improves the atmospheric dynamic field. This study presents radar DA experiments using a numerical prediction model to enhance the wind, water vapor, and hydrometeor mixing ratio information. The impact of radar DA on precipitation prediction is analyzed separately for each radar component. Assimilating radial velocity improves the dynamic field, while assimilating hydrometeor mixing ratio reduces the spin-up period in cloud microphysical processes, simulating initial precipitation growth. Assimilating water vapor mixing ratio further captures a moist atmospheric environment, maintaining continuous growth of hydrometeors, resulting in concentrated heavy rainfall. Overall, the radar DA experiment showed a 32.78% improvement in precipitation forecast accuracy compared to experiments without DA across four cases. Further research in related fields is necessary to improve predictions of mesoscale heavy rainfall in South Korea, mitigating its impact on human life and property.

인공위성 고도계 자료(1993-2017년)를 이용하여 탐지‧추적‧분류한 동해 중규모 소용돌이의 통계적 특성 (Statistical Characteristics of East Sea Mesoscale Eddies Detected, Tracked, and Grouped Using Satellite Altimeter Data from 1993 to 2017)

  • 이경재;남성현;김영규
    • 한국해양학회지:바다
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    • 제24권2호
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    • pp.267-281
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    • 2019
  • 활발한 중규모 변동성으로 인해 해양 환경과 순환의 극심한 변화를 초래하는 동해 전역에서 장기간(1993-2017년) 수집된 인공위성 고도계 자료와 2015-2017년 기간의 4차례 승선 조사로 수집된 현장 관측 자료를 분석하여 중규모 소용돌이의 통계적 특성을 규명하였다. 동해 전역에서 해당 기간 동안 총 1,008개의 중규모 소용돌이를 탐지 추적 정의하고, 이를 27개의 그룹으로 분류하여, 전체 평균 및 각 그룹별 평균 지속기간(L, 일), 진폭(H, m), 반경(R, km), 단위 면적당 강도(EI, $cm^2/s^2/km^2$), 타원율(e), 운동에너지(EKE, TJ), 가용위치에너지(APE, TJ) 및 전파 방향을 산출하였다. 인공위성 고도계 자료로부터 산출된 소용돌이의 중심, 경계, H 각각을 현장 관측 자료로부터 산출된 해당 수치와 비교하여 각각에 대한 불확실성을 중심 오차 2-10 km, 경계 오차 10-20 km, 진폭 오차 0.6-5.9 cm로 추정하였다. 정의된 모든 소용돌이들의 전기간 평균 L, H, R, EI, e, EKE, APE는 각각 $95{\pm}104$일, $3.5{\pm}1.5cm$, $39{\pm}6km$, $0.023{\pm}0.017cm^2/s^2/km^2$, $0.72{\pm}0.07$, $23{\pm}21TJ$, $588{\pm}250TJ$로서 대양에 비해 전반적으로 L이 짧고, H, R은 작으며, EI는 강하고, EKE는 낮게, APE는 높게 나타났다. 또, 대양에서와 같은 뚜렷한 서향 전파 특성을 보이지 않고, 대체로 해류를 따라 이동하는 특성을 보였다. 아극전선(subpolar front)을 기준으로 남부 소용돌이 그룹의 L, H, R, EI, EKE, APE가 북부 그룹에 비해 더 길고, 크고, 강하며, 높고, 평균 해류 방향으로 더 멀리 이동하는 특성을 보였다. 뿐만 아니라 특정 방향으로의 이동이 뚜렷하지 않은 4개 그룹들(Wonsan Warm Eddy, Wonsan Cold Eddy, Western Japan Basin Warm Eddy, Northern Subpolar Frontal Cold Eddy groups)과 상대적으로 크고, 강하며, 높은 H, EI, EKE, APE에도 불구하고 오래 지속되지 않는(짧은 L) 특성을 보이는 3개 그룹들(Yamato Coastal Warm Eddy, Central Yamato Warm Eddy, Eastern Japan Basin Coastal Warm Eddy groups)도 제시하였다. 인공위성 고도계만으로는 잘 탐지되기 어려운 작은 규모의 소용돌이가 존재하는 동해 북부 해역에서는 소용돌이 그룹이 정의되지 않았으며, 본 연구에서 제시된 동해 평균 소용돌이 특성치의 과대추정 가능성이 토의되었다. 본 연구를 통해 1) 기존에 비교적 잘 알려진 울릉 난수성 소용돌이(Ulleung Warm Eddy)와 독냉수성 소용돌이(Dok Cold Eddy) 그룹 외에도 Hokkaido Warm Eddy, Yamato Rise Warm Eddy와 같은 그룹들을 새로 정의하였고, 2) 대양의 중규모 소용돌이에 비해 전반적으로 그 L이 짧고, H, R은 작고, EKE는 낮으나, EI는 강하고, APE는 높으며, 서향 전파가 뚜렷하지 않은 동해의 중규모 소용돌이 특성을 규명했으며, 3) 동해 내에 그룹별로 상이한 중규모 소용돌이 그룹의 특성을 제시하였다.

Nudging of Vertical Profiles of Meteorological Parameters in One-Dimensional Atmospheric Model: A Step Towards Improvements in Numerical Simulations

  • Subrahamanyam, D. Bala;Rani, S. Indira;Ramachandran, Radhika;Kunhikrishnan, P. K.
    • Ocean Science Journal
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    • 제43권4호
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    • pp.165-173
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    • 2008
  • In this article, we describe a simple yet effective method for insertion of observational datasets in a mesoscale atmospheric model used in one-dimensional configuration through Nudging. To demonstrate the effectiveness of this technique, vertical profiles of meteorological parameters obtained from GLASS Sonde launches from a tiny island of Kaashidhoo in the Republic of Maldives are injected in a mesoscale atmospheric model - Advanced Regional Prediction System (ARPS), and model simulated parameters are compared with the available observational datasets. Analysis of one-time nudging in the model simulations over Kaashidhoo show that incorporation of this technique reasonably improves the model simulations within a time domain of +6 to +12 Hrs, while its impact on +18 Hrs simulations and beyond becomes literally null.

수치모의를 통한 미세규모 순환과 확산에 대한 예측 (Predictions of Local Circulation and Dispersion with Microscale Numerical Model)

  • 안광득;이용희;장동언;조천호
    • 한국군사과학기술학회지
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    • 제6권4호
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    • pp.147-158
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    • 2003
  • The prediction of wind field is very important fact in the radioactive and chemical warfare. In spite of advanced numerical weather prediction modelling and computing technology, the high resolution prediction of wind field is limited by the very high integration costs. In this study we coupled the mesoscale numerical model and microscale diagnostic numerical model with minimized integration costs. This coupled model has not only the ability of prediction of high resolution wind field including complex building but also microscale pollutant diffusion fields. For military operation this system can help making a practical and cost-effective decision in a battle field.

중규모 국지순환에서 이산화황의 농도예측에 관한 연구 (A Study on the Prediction of SO2 Concentration in local Circulation of Mesoscale)

  • 이화운;김유근;장은숙
    • 한국환경과학회지
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    • 제5권3호
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    • pp.277-284
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    • 1996
  • The Characteristics of atmospheric flow and dispersion of air pollutants in the mountainous coastal area were studied using two-dimensional model by the combination of land-sea breezes and transport. The pollutants emitted into the simulated wind field in considering with the mesoscale local circulations. The typical effects of land-sea breezes and tophography of coastal area on the dispersion are discussed in detail, and the model is proved as an useful tool to pridict real time pollutant transport by the results of application studies in Pusan, Korea where the urbanized coastal area with mountainous topography. It was found that sulfur dioxide ($SO_2$) are differently transported and concentrated as going inland by the influence of the sea breeze with topographic changes. Key words : land-sea breezes, sulfur dioxide, dispersion, coastal area.

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