• Ocean Systems Engineering
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• 제2권2호
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• pp.83-97
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• 2012

In the present work, design procedure and computer simulation of an AUV are documented briefly. The design procedure containing the design of propulsion system and CFD simulation of hydrodynamics behavior of the hull leads to achieve an optimum mechanical performance of AUV system. After designing, a comprehensive one dimensional model including motor, propeller, and AUV hull behavior simulates the whole dynamics of AUV system. In this design, to select the optimum AUV hull, several noses and tails are examined by CFD tools and the brushless motor is selected based on the first order model of DC electrical motor. By calculating thrust and velocity in functional point, OpenProp as a tool to select the optimum propeller is applied and the characteristics of appropriate propeller are determined. Finally, a computer program is developed to simulate the interaction between different components of AUV. The simulation leads to determine the initial acceleration, final velocity, and angular velocity of electrical motor and propeller. Results show the final AUV performance point is in the maximum efficiency regions of DC electrical motor and propeller.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.1-18
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• 2013

The typhoon wind characteristics designing for buildings or bridges located in complex terrain and typhoon prone region normally cannot be achieved by the very often few field measurement data, or by physical simulation in wind tunnel. This study proposes a numerical simulation procedure for predicting directional typhoon design wind speeds and profiles for sites over complex terrain by integrating typhoon wind field model, Monte Carlo simulation technique, CFD simulation and artificial neural networks (ANN). The site of Stonecutters Bridge in Hong Kong is chosen as a case study to examine the feasibility of the proposed numerical simulation procedure. Directional typhoon wind fields on the upstream of complex terrain are first generated by using typhoon wind field model together with Monte Carlo simulation method. Then, ANN for predicting directional typhoon wind field at the site are trained using representative directional typhoon wind fields for upstream and these at the site obtained from CFD simulation. Finally, based on the trained ANN model, thousands of directional typhoon wind fields for the site can be generated, and the directional design wind speeds by using extreme wind speed analysis and the directional averaged mean wind profiles can be produced for the site. The case study demonstrated that the proposed procedure is feasible and applicable, and that the effects of complex terrain on design typhoon wind speeds and wind profiles are significant.

• 한국정보통신학회논문지
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• 제17권5호
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• pp.1160-1167
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• 2013

네트워크 및 컴퓨팅 기술의 발달로 실생활에서 일어나는 다양한 현상을 수치적으로 계산하고 분석할 수 있는 웹 시뮬레이션 서비스가 활발히 사용되고 있다. 이 논문에서는 웹 기반 열유체 시뮬레이션을 제공하는 e-AIRS(e-Science Aerospace Integrated Research System) 서비스의 개선 및 활용에 대해 기술한다. 2008년부터 서비스된 e-AIRS는 안정성에 일부 문제가 있어 사용자가 종종 원활한 시뮬레이션을 수행하기 어려움이 있었다. 이 문제를 해결하기 위하여 화면 갱신 방법 개선, 서비스 분산처리, 개인별 시뮬레이션 작업량 할당, 데이터 로딩 시간 감소, 등의 개선 작업을 수행하였다. 개선 후 사용자가 110명에서 606명으로 증가했음에도 안정성에 대한 요구사항은 감소하여 효과적으로 개선이 이루어졌음을 알 수 있다. 매 학기마다 분석되는 시뮬레이션 서비스 활용 내역 및 사용자 요구사항은 보다 나은 서비스를 제공하기 위해 사용될 것이다.

• 한국해안·해양공학회논문집
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• 제23권6호
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• pp.466-473
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• 2011

온배수의 수중 방류 시 강한 방류 모멘텀 플럭스와 부력 플럭스에 의해 수중제트 인근에는 부력제트가 지배적인 근역이 형성되며, 이러한 근역을 해석하는 도구로써 비정수압 RANS 방정식을 적용한 전산유체역학(CFD) 모델을 이용하여 근역에 대한 적용성을 검토해 보았다. 과거 연구된 바 있는 원형 부력제트 수리실험과 유사한 조건으로 모델을 구성하고 정류시의 수평 부력 제트 경우와 가로흐름시 수직 부력 제트 경우에 대해 수치 실험을 수행하였다. CFD 수치실험의 결과는 수리실험 및 해석해 모델(CorJET)의 결과와 무차원화한 중심 궤적 및 희석율에 대해 비교 검증하였는데, 실제 수리실험의 결과와 잘 일치하는 것으로 나타났다. CFD 모델은 현재 근역 해석해 모델과 광역 준3차원 해수유동 모델이 가지고 있는 한계를 모두 보완할 수 있어 수중방류 온배수 영향해석에 적합한 모델이며, 본 연구를 통해 근역해석의 적합성을 확인하였으므로 향후 계산효율이 확보된다면 수중방류 온배수의 이동 및 확산 해석 도구로써 널리 활용될 것으로 기대된다.

• 한국해양공학회지
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• 제35권1호
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• pp.13-23
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• 2021

Since the introduction of the mandatory energy efficiency design index (EEDI), several studies have been conducted on the maneuverability of waves owing to the decrease in engine power. However, most studies have used the mean wave force during a single cycle to evaluate maneuverability and investigated the turning performance. In this study, we calculated the external force in accordance with the angle of incidence of the wave width and wavelengths encountered by KVLCC2 (KRISO very large crude-oil carrier) operating at low speeds in regular waves using computational fluid dynamics (CFD). We compare the model test results with those published in other papers. Based on the external force calculated using CFD, an external force that varies according to the phase of the wave that meets the hull was derived, and based on the derived external force and MMG control simulation, a maneuvering simulation model was constructed. Using this method, a weather vaning simulation was performed in regular waves to evaluate the course-keeping ability of KVLCC2 in waves. The results confirmed that there was a difference in the operating trajectory according to the wavelength and phase of the waves encountered.

• 대한안전경영과학회지
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• 제14권3호
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• pp.93-100
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• 2012

The transmission of the world Installed in an Office occurs through the air. Preventing that transmission, especially in indoor environments like those in airplanes, schools and offices, is a major public health concern. in this study the real situation of lab which is consist of dilution, Ultraviolet-C based air sterilization system. This model include indoor microbe transport which is generated human source. a computer simulation was performed to determine if such simulation can be used effectively to predict the more accurate, but difficult to perform, actual physical experiment. Result show that CFD can be modeled microbe transport effectively and it can be visualized microbe transport separation from flow streamline. also it make a good prediction of microbe transport.

• 한국해양공학회지
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• 제31권5호
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• pp.371-377
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• 2017

This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6DOF (degrees-offreedom) motion analysis for an underwater vehicle. Hydrodynamic derivatives were derived from second-order modulus expansion and composed of the added mass, and linear and nonlinear damping coefficients. The added mass coefficients were analytically obtained using the potential theory. All of the linear and nonlinear damping coefficients were determined using CFD simulation, which were performed for various cases based on the actual operating condition. Then, the linear and nonlinear damping coefficients were determined by fitting the CFD results, which referred to 6DOF forces and moments acting on an underwater vehicle, with the least square method. To demonstrate the applicability of the current study, 6DOF simulations for three different scenarios (L-, U-, and S-turn) were carried out, and the results were validated on the basis of physical plausibility.

• Wind and Structures
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• 제19권6호
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• pp.649-663
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• 2014

The present paper discusses the characteristics of unsteady aerodynamic forces on long-span curved roofs. A forced vibration test is carried out in a wind tunnel to investigate the effects of wind speed, vibration amplitude, reduced frequency of vibration and rise/span ratio of the roof on the unsteady aerodynamic forces. Because the range of parameters tested in the wind tunnel experiment is limited, a CFD simulation is also made for evaluating the characteristics of unsteady aerodynamic forces on the vibrating roof over a wider range of parameters. Special attention is paid to the effect of reduced frequency of vibration. Based on the results of the wind tunnel experiment and CFD simulation, the influence of the unsteady aerodynamic forces on the dynamic response of a full-scale long-span curved roof is investigated on the basis of the spectral analysis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.843-846
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• 2002

Unlike ordinary train, the HST(High Speed Train) is operated at a very high speed, which may cause pressure transient problems when the HST is passing through a station. In the present study, the wind pressure caused by the passing HST was measured in the Cheonan HST station and compared with the numerical simulations. For the measurement, the HST was passing through the station at speeds of 240 km/h north bound and 150 km/h south bound. MEMS based differential pressure transducers are used to measure pressure variation at various locations in the station. It is shown from the results that measured data are in good agreement with CFD simulation with moving mesh technique for the train movement. With the present validation of CFD simulation, the CFD simulation may effectively aid the design of future HST station.

• Korean Chemical Engineering Research
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• 제46권5호
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• pp.922-930
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• 2008

질소산화물($NO_x$) 저감을 위한 선택적 무촉매 환원(SNCR; selective non-catalytic reduction) 공정의 성능은 유속, 반응온도 그리고 반응물간의 혼합과 같은 공정변수에 민감하다. 따라서 효율적인 SNCR 공정의 설계와 운전을 위하여 속도장, 온도장, 및 화학물질들의 농도 분포에 대한 이해가 필수적이다. 본 연구에서는 150 kW LPG 버너가 장착되고, 요소용액을 환원제로 사용하는 파일럿 규모 SNCR 공정에 대하여 액적모델과 결합된 2차원 난류반응흐름 전산유체역학(CFD; computational fluid dynamics) 모델을 개발하고, 이 모델은 실험결과를 통하여 검증된다. 난류반응 CFD 모델에서는 $NO_x$저감율과 $NH_3$-slip을 예측하기 위하여 7개 반응식으로 이루어진 요소용액과 $NO_x$와의 반응기작을 이용한다. 이러한 모델을 이용한 CFD 모사결과는 온도와 NSR(normalized stoichiometric ratio)에 따른 $NO_x$ 저감율에서 실험결과와 최대 20% 이내에서 차이를 보여주고 있으며, $NH_3$-slip에 대하여는 실험결과와 모사결과 사이에 유사한 경향성을 얻었다.