• Wind and Structures
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• 제22권4호
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• pp.503-524
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• 2016

The suitability of Computational Fluid Dynamics (CFD) simulations on the built environment for the purpose of estimating average roughness characteristics and for studying wind flow patterns within the environment is assessed. Urban models of various levels of complexity are considered including an empty domain, array of obstacles arranged in regular and staggered manners, in-homogeneous roughness with multiple patches, a semi-idealized built environment, and finally a real built environment. For each of the test cases, we conducted CFD simulations using RANS turbulence closure and validated the results against appropriate methods: existing empirical formulas for the homogeneous roughness case, empirical wind speed models for the in-homogeneous roughness case, and wind tunnel tests for the semi-idealized built environment case. In general, results obtained from the CFD simulations show good agreement with the corresponding validation methods, thereby, giving further evidence to the suitability of CFD simulations for built environment studies consisting of wide-ranging roughness. This work also provides a comprehensive overview of roughness modeling in CFD-from the simplest approach of modeling roughness implicitly through wall functions to the most elaborate approach of modeling roughness explicitly for the sake of accurate wind flow simulations within the built environment.

• 대한화학회지
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• 제19권5호
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• pp.294-303
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• 1975

直線 衝突모형을 써서 三原子 置換反應 $A+B-C{\to}A-B+C$의 反應確率을 全體 에너지의 函數로 計算하였다. 使用한 포텐셜 에너지 亦是 極히 單純한 理想的인 것이다. 세原子의 質量이 모두 같은 경우에 대하여 數値로 結果를 얻어서 더욱 더 간단한 모형을 쓴 다른 硏究者들의 結果와 比較하여 定性的으로 더 나음을 알았다.

• 한국방재학회 논문집
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• 제6권2호
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• pp.9-15
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• 2006

토목구조물은 주로 안전성을 위주로 설계되어 왔으나 최근 들어 토목기술에 대한 환경친화적 측면이 중시되어지는 가운데 구조물의 사용성과 안정성의 비중이 커져가고 있다. 또한 기술의 발달로 재료의 고강도화가 이루어져 구조부재 자체의 크기나 단면적이 줄어들었는데 이는 교량구조물의 과도한 처짐과 진동을 동시에 야기했다. 따라서 본 연구에서는 교량 구조물의 통과주체가 되는 차량동하중과 인체보행하중이 교량에 미치는 처짐과 진동에 대한 영향을 적용 가능한 가장 이상화 된 모델링을 찾아내어 진동영향평가 할 수 있도록 하기 위한 연구를 수행하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.538-544
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• 2009

A vibration excitation system was designed and built of forced vibration experiments for using stepping motor and load cell. The identified flutter derivatives of the thin-plate acrylic model were very close to the analytical results of the idealized plate presented by Theodorsen. Five types of sectional models were tested in the wind tunnel using the proposed forced vibration method. To investigate the frequency, amplitude and angle of attack effects on flutter derivatives.

• 천문학회보
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• 제42권2호
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• pp.55.2-55.2
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• 2017

We present a numerical code for the random scattering histories of Lyman alpha photons in the intergalactic medium. The numerical code calculates the radiative transfer under generic three dimensional density, ionization fraction, and peculiar velocity fields based on N-body + radiation transfer simulations of the epoch of reionization. The code is tested with models having analytical solutions, which have idealized geometry and simplified velocity fields. The emergent line profiles can give constraints to the ionization structure around Lyman alpha sources in the early universe.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 봄 학술발표회논문집
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• pp.191-198
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• 1993

This paper presents the analysis briefs to evaluate the structural adequacy of the KMRR spent fuel storage racks which stack modules in three layers. The seismic analysis models are idealized to consider the overall dynamic motions such as rocking, sliding and liftoff in the event of an postulated earthquake. The displacement time histories of the floor obtained from the floor response spectra in three orthogonal directions are simultaneously applied to the nonlinear seismic model of the structure with gap and friction elements.

• 한국추진공학회지
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• 제13권2호
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• pp.54-63
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• 2009

이상화된 하이브리드 로켓모터 내부의 난류 유동 및 온도장의 발달과정을 대와류모사 기법을 사용하여 살펴보았다. 화학반응 및 밀도의 변화를 고려하지는 않았으나, 물리적으로 타당한 난류 입구조건과 22,500의 높은 Reynolds수 및 regression에 의한 벽면분출을 고려하여, 벽면근처에서 일어나는 난류유동의 시간 특성을 파악하였다. 하이브리드 모터 내부에서 발생한 혼합전단층의 불안정성에 기인한 특정 시간스케일(St~0.5)이 수동스칼라장에서 검출되지 않았다는 사실은 난류 온도장 해석에 난류 Prandtl 수를 상수로 가정하는 기존의 접근방식이 상당한 오차를 발생시킬 수 있다는 것을 의미한다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.276-276
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• 2022

Estuarine dams are constructed for securing freshwater resources, flood control, and improving upstream navigability. However, their impact on estuarine currents, stratification, and sediment fluxes is not well understood. To develop a general understanding, an idealized modeling study was carried out. Tide and river forcing were varied to produce strongly stratified, partially mixed, periodically stratified, and well-mixed estuaries. Each model ran for one year. Next, the models were subject to the construction of an estuarine dam and run for another year. Then, the pre- and post-dam conditions were compared. Results showed that estuarine dams can amplify the tidal range and reduce the tidal currents. The post-dam estuaries tended to be a salt wedge during freshwater discharge and a bay during no freshwater discharge. For all estuaries, the estuarine turbidity maximum moved seaward, and the suspended sediment concentrations tended to decrease. In terms of sediment flux mechanisms, the estuarine dam increased the seaward river runoff for cases with strong river, and increased the landward tidal pumping for cases with strong tides.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.189-197
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• 1996

In this study, the crashworthiness analysis was carried out for the hat type section side rails which had an important role of absorbing the impact energy during frontal crash. In case of a tapered hat type section model, numerical simulation models and test models were designed with varing design variables; welding pitch, taper angle, initiator shape, initiator location. The effect of variation of the design variables was investigated by quasi-static and dynamic test and numerical simulation.

• Computers and Concrete
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• 제4권4호
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• pp.259-272
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• 2007

A method based on the lower-bound theorem of limit analysis is presented for the capacity assessment of nodal zones in strut-and-tie models. The idealized geometry of the nodal zones is formed by the intersection of effective widths of the framing struts and ties. The stress distribution is estimated by dividing the nodal zones into constant stress triangles separated by lines of stress discontinuity. The strength adequacy is verified by comparing the biaxial stress field in each triangle with the corresponding failure criteria. The approach has been implemented in a computer-based strut-and-tie tool called CAST (Computer-Aided Strut-and-Tie). An application example is also presented to illustrate the approach.