• 한국해양공학회지
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• 제20권5호
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• pp.15-22
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• 2006

A finite-volume method using multi-block grid technique has been developed in order to investigate the flow field around multi-body. Here the matching grids are used at the interface between blocks and the boundary conditions are imposed there to exchange physical values across the interface. For the test problems, the laminar viscous flaw around one-and two-cylinder are simulated and the results are compared with experiments and other numerical results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.111-114
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• 2004

CFD code that simulates stator-rotor interactions is developed applying parallel computing method. Modified Multi-Block Grid System which enhances perpendicularity in grid and is appropriate in parallel processing is introduced and Patched Algorithm is applied in sliding interface which is caused by movement of rotor. The experimental model in the turbo-machine is composed of 11 stators and 14 rotors. Analyses on two test cases which are one stator - one rotor model and three stators - four rotors model are performed. The results of the two cases have been compared with the experimental test data.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2006년도 춘계학술발표대회
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• pp.153-156
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• 2006

본 논문에서는 H.264 표준화 기구인 Joint Video Team(JVT) 권고안의 정수 단위 화소 움직임 예측을 위한 Unsymmetrical-cross Multi-Hexagon-grid Search(UMHexagonS) 알고리즘에서 Uneven Multi-Hexagon-grid Search(UMHGS) 부분을 개선한 알고리즘을 제안한다. 제안하는 알고리즘은 이전 프레임의 동일위치 또는 상위 모드에서 이미 선택된 움직임 벡터(MV: Motion Vector)를 이용하여 신호 대 잡음 비(PSNR: Peak Signal to Noise Ratio) 및 평균 비트 율(Average Bitrates)을 유지하면서, 현재 매크로블록의 검색영역을 줄이는 것이 가능하다. 제안하는 알고리즘의 성능은 Full Search Block Matching Algorithm(FSBMA) 및 UMHexagonS 알고리즘의 integer pel 에 대한 SAD(Sum of Absolute Difference) 연산횟수로 비교평가 하였다. 그 결과, FSBMA 에 비하여 평균 97.64%, UMHexagonS 에 비하여는 평균 17.48%의 연산횟수를 감소시키는 우수함을 보였다.

• 대한기계학회논문집B
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• 제21권3호
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• pp.414-426
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• 1997

Numerical computations were conducted to characterize the three-dimensional laminar flow through an injector orifice having an inclined angle of 30 .deg.. For this study, the incompressible Navier-Stokes equations in generalized curvilinear coordinates, using a pseudocompressibility approach for continuity equation, were solved. The computations were performed using the finite difference implicit, approximately factored scheme of Beam and Warming and multi-block grids of complete continuity at block interfaces. The multi-block computations were validated for the steady state using direct comparison of multi-block solutions with equivalent single-block ones, including 2-D 180.deg. TAD and 3-D 90.deg. pipe bend. The comparisons between the numerical solutions and the flow field measurements for a tube with sudden contraction were presented in this work for solution validation. Computational results showed the nature of complex flow fields within the inclined injector orifice, including strong pressure-driven secondary flows in the cross stream induced by the effect of streamline curvature. In addition, asymmetric secondary flows were induced in the Reynolds number range above assumed laminar flow regime considered. However, turbulence calculations and grid dependency studies are needed for more accurate computations.

• 한국항공우주학회지
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• 제31권6호
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• pp.8-16
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• 2003

3차원 비정상, 비압축성 Navier-Stokes 방정식 해석코드를 이용하여, 초소형 비행체 주위에 형성되는 저 레이놀즈수 유동장의 공력 특성을 연구하였다. 비정상 유동장의 효율적인 계산을 위하여, 개발된 코드는 MPI 프로그래밍 기법을 이용하여 병렬처리 하였으며, single partitioning 방법을 적용하여 3차원 형상에 대한 multi-block 격자계를 효율적으로 해석 하였다. 비교적 형상이 복잡하지 않은 초소형 비행체 주위 날개에 대해 해석한 후 초소형 비행체 전 형상에 대해 받음각을 변화시키며 공력계수 및 정안정성을 살펴보았다. 해석 결과, 서울대학교 미소공기역학실험실에서 수행한 아음속 풍동 실험데이터와 비교하여 보았을 때 대체로 잘 일치하였으며, 개념 설계한 비행체가 공기역학적으로 정안정성을 갖고 있음을 보일 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.189-192
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• 2002

In this paper, the submarine model, called DARPA SUBOFF model, has been numerically analyzed to investigate the aerodynamic forces variation in terms of angle of attacks and yaw angles. The SUBOFF model is consisted of the three parts : axisymmetric body, fairwater, and four symmetric stern appendages. Three dimensional unsteady incompressible Wavier-Stokes equation was used on curvilinear multi-block grid system. To validate the present code, the SUBOFF tare hull and an ellipsoid at angle of attacks of $10^{\circ}\;and\;30^{\circ}$ were simulated and a good agreement with experiments was obtained. After the code validation, the flows over SUBOFF model were simulated at three different angle of attacks and yaw angles. The variation of aerodynamic forces in terms of angle of attack and yaw angle were calculated. Also, to understand the flow features around a submarine with variation of yaw and attack angle, the pressure contours and streamlines were plotted.

• 한국전산유체공학회지
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• 제11권1호
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• pp.1-7
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• 2006

Numerical investigation of a centrifugal compressor volute having a modified straight conical duct hill been made. Three-dimensional Reynolds-Averaged Navier-Stokes equations with $k-{\varepsilon}$ turbulence equation are solved To avoid coordinate singularity at the central axis of the duct, multi-block H-type grid is generated on the circular cross-sections of the volute and stretched toward the solid wall boundary. We obtained numerical results with three different mass flow rates at the volute inlet, namely, with the inlet conditions that give small, medium and large mass flow rates at the outlet of the conical duct. Agreement with the experimental results is observed.

• 한국전산유체공학회지
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• 제21권2호
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• pp.25-31
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• 2016

In this paper, a study on the development of OpenFOAM grid generation program for two-dimensional flow analysis is described. By using the pre-processor(eMEGA) of EDISON_CFD system, grids for OpenFOAM flow calculation were obtained. Resultant two-dimensional grids were used to calculate flow fields by applying simpleFoam, one of the OpenFOAM's popular solvers, and the obtained flow results were compared with theoretical and experimental data available. Also grids generated by present program were compared with grids by a commercial pre-processor Pointwise for the purpose of verification. Verification work includes three cases(single block, O-type single block, and multi block grid), and all results show reasonable matches. According to the current achievement, it can be concluded that OpenFOAM grid can be constructed conveniently by using eMEGA with GUI.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.183-183
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• 2003

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.145-151
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• 1999

An Interactive grid generation program(KGRID) with graphical user interface(GUI) has been improved. KGRID works on the UNLX environment and GUI has been implemented with OSF/Motif and X Toolkit and the graphics language is Open GL for visualization of the 3D objects. It supports more convenient user environment to generate 2D and 3D multi-block structured grid systems. It provides various useful field grid generation methods, which are the algebraic methods, the elliptic partial differential equations method and the predictor-corrector method. It also supports 3D surface grid generation with NURBS(Non-Uniform Rational B-Spline) and various stretching functions to control grid points distribution on curves and surfaces. And some menus are added to perform flexible management, for the objects. We generated surface and field grid system about full aircraft configuration using KGRID. The performance and stability of the KGRID is verified through the generation of the grid system about a complex shape.