• 한국전산유체공학회지
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• 제19권3호
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• pp.85-90
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• 2014

The purpose of this study is to develop a new Meshless Method to solve 2-D compressible flow problems numerically. This paper includes a revised Least Square method that improves robustness compared with its original version by removing excessive numerical oscillation which occurs when points are randomly distributed. Numerical analyses of hypersonic flow over a blunt body were carried out using the method, then robustness, accuracy and convergence of their results were compared with those obtained from the original method.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.760-763
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• 2010

강내탄도 성능 해석의 정확도를 높이기 위해서 1차원 해석 코드를 2차원 및 3차원으로 확장시키는 작업이 필요하다. 다차원 확장 시 이동경계면 해석에 Cut Cell Method를 적용하였다. 이에 high resolution 기법인 MUSCL-Hancock을 선택하였고 free piston problem에 적용하여 그 타당성을 검증하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1064-1081
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• 2014

This paper presents a numerical analysis of slamming and whipping using a fully coupled hydroelastic model. The coupled model uses a 3-D Rankine panel method, a 1-D or 3-D finite element method, and a 2-D Generalized Wagner Model (GWM), which are strongly coupled in time domain. First, the GWM is validated against results of a free drop test of wedges. Second, the fully coupled method is validated against model test results for a 10,000 twenty-foot equivalent unit (TEU) containership. Slamming pressures and whipping responses to regular waves are compared. A spatial distribution of local slamming forces is measured using 14 force sensors in the model test, and it is compared with the integration of the pressure distribution by the computation. Furthermore, the pressure is decomposed into the added mass, impact, and hydrostatic components, in the computational results. The validity and characteristics of the numerical model are discussed.

• 설비공학논문집
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• 제25권10호
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• pp.562-567
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• 2013

1D-numerical analysis of the network algorithm with the orifice equation for the relationship between pressure difference and flowrate has been mostly used to analyse leakage flow at the gap. In this study, a 3D-numerical method applying momentum loss model to the gap region in the computational domain is represented to reflect effectively the effect of leakage flow by determining the proportion of pressure difference to air passage velocity. While the 3D-numerical method is verified through the computation of the two compartments model, the numerical analysis of the stack effect in a building stairway is performed. As the temperature of air outside drops, the pressure in the upper stairway and leakage flowrate through the gap in the door rise. The change of gap area does not have an effect on pressure in the stairway for the analysis conditions.

• Structural Engineering and Mechanics
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• 제18권1호
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• pp.59-78
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• 2004

This paper is devoted to illustrate some numerical procedures to solve the boundary equilibrium problems of three-dimensional solids that are subjected to thermal strains. The constitutive equations take into account the bounded tensile strength of the material and they are presented in the framework of non-linear elasticity and small strains. The associated equilibrium problem is solved numerically by means of the finite element method and the numerical techniques, i.e. the Newton-Raphson method and the secant method, are revised in order to assure the solution convergence of the discretized problem. Some numerical examples are illustrated.

• Structural Engineering and Mechanics
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• 제43권3호
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• pp.321-336
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• 2012

As an improvement on the isoparametric element method, the derivation presented in this paper is close to that done by Wang (1990) for the 2-D finite element. We extend this idea to solve 3-D crack problems in this paper. A new displacement modelling is constructed with local solutions of three-dimensional cracks and a quasi-compatible isoparametric element for three-dimensional fracture mechanics analysis is presented. The stress intensity factors can be solved directly by means of the present method without any post-processing. A new method for calculating the stress intensity factors of three-dimensional cracks with complex geometries and loads is obtained. Numerical examples are given to demonstrate the validity of the present method. The accuracy of the results obtained by the proposed element is demonstrated by solving several crack problems. The results illustrate that this method not only saves much calculating time but also increases the accuracy of solutions. Because this quasi-compatible finite element of 3-D cracks contains any singularities and easily meets the requirement of compatibility, it can be easily implemented and incorporated into existing finite element codes.

• 한국해안·해양공학회논문집
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• 제24권1호
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• pp.48-57
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• 2012

본 연구에서는 고립파를 저감시키기 위한 저감공으로 본문 중에서 제시하는 공진장치를 직선배치된 기존의 방파제와 직사각형항만의 입구부에 각각 부착하고, 이에 따른 고립파의 제어능을 검토하기 위해 3차원수리모형 실험 및 3차원수치해석을 수행하였다. 수치해석에서는 3차원수치파동수조를 이용하는 3차원혼상류해석법의 TWOPM-3D를 적용하였고, 얻어진 수치해석결과와 수리실험결과를 비교 분석하여 본 수치해석법의 타당성을 검증하였다. 또한, 공진장치가 부착되지 않은 경우와 대비 고찰하여 고립파의 제어에 대한 공진장치의 제어능을 다각도로 검토한 결과, 그의 유효성을 충분히 확인할 수 있었다.

• 한국해양공학회지
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• 제28권3호
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• pp.227-235
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• 2014

Using a 3-D numerical scheme (LES-WASS-3D) that considered wave-structure-sandy seabed interactions in a 3-D wave field, we analyzed the wave reflection and hydraulic characteristics inside a slit caisson with two chambers in a 3-D oblique wave field. To verify the 3-D numerical analysis method suggested in this study, we compared the numerical results with existing experimental results and found good agreement. The numerical analysis revealed that a standing wave field is generated on the front side of the slit caisson due to the effect of wave reflection. For incident waves propagating perpendicular to the slit caisson, the nodes and anti-nodes of the standing wave are apparent and symmetrical. However, in an oblique wave field, as the incident wave angle decreases, the nodes and anti-nodes of the standing wave become ambiguous and unsymmetrical. It was also found that the wave reflection coefficient decreases as the incident wave angle decreases. It can be pointed out that as the incident wave angle decreases, the turbulent intensity in the chamber increases. Thereby, the increased wave energy dissipation by the increased turbulent intensity reduces the rate of wave reflection. In addition, a strong turbulent intensity generally occurs in the first chamber.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.315-319
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• 2010

The near wake of square section cylinders with different corner radii is studied by numerical method to investigate the influence of corner radius. Eight models, R/D=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 (R is the corner radius and D is the characteristic dimension of the body) at Re=500 were studied. The numerical results of St, CD and CL at R/D=0 and R/D=0.5 were compared with experiments to prove the feasibility and also investigate the trend of flow phenomena by the various radius corners. Results indicate that, as R/D ratio is increased, the Strouha lnumber is increased, the minimum pressure point on the cylinder surface moved own stream. The calculated results shows that between R/D=0.15 to R/D=0.3 have CD and CL.

• 항공우주시스템공학회지
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• 제1권1호
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• pp.67-72
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• 2007

In this paper, numerical results for 3-D supersonic turbine flow have been firstly compared with the experimental results to verify results computed by $Fine^{TM}/Turbo$. It was found that $Fine^{TM}/Turbo$ can accurately predict flow characteristics within supersonic turbine. Next, an grid system for 3D turbine flow was optimized selected through grid independency test. Finally, the effect of axial gap between rotor and nozzle and chamfer angle of blade edge on the flow characteristics within 3-D supersonic turbine was analyzed with Frozen Rotor method.