• Title, Summary, Keyword: 오픈폼

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Numerical Simulations of Added Resistance and Motions of KCS in Regular Head Waves (선수 규칙파 중 KCS의 부가저항 및 운동성능 수치해석)

  • Seo, Seonguk;Park, Sunho
    • Journal of the Society of Naval Architects of Korea
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    • v.54 no.2
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    • pp.132-142
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    • 2017
  • As the International Maritime Organization (IMO) recently introduced the Energy Efficiency Design Index (EEDI) for new ships building and the Energy Efficiency Operational Indicator (EEOI) for ship operation, thus an accurate estimation of added resistance of ships advancing in waves has become necessary. In the present study, OpenFOAM, computational fluid dynamics libraries of which source codes are opened to the public, was used to calculate the added resistance and motions of the KCS. Unstructured grid using a hanging-node and cut-cell method was used to generate dense grid around a wave and KCS. A dynamic deformation mesh method was used to consider the motions of the KCS. Five wavelengths from a short wavelength (${\lambda}/LPP=0.65$) to a long wavelength (${\lambda}/LPP=1.95$) were considered. The added resistance and the heave & pitch motions calculated for various waves were compared with the results of model experiments.

A Study on Spatial Distributions of Courant Number and Numerical Efficiency of LTS Method in Calculation of Ship Resistance Using Structured and Unstructured Meshes (정렬 및 비정렬 격자를 이용한 선박 저항 계산에서 Courant 수의 공간 분포 및 LTS 기법의 효율성에 관한 연구)

  • Lee, Sang Bong;Paik, Kwang-Jun;Park, Dong Woo
    • Journal of the Society of Naval Architects of Korea
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    • v.54 no.2
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    • pp.83-89
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    • 2017
  • Numerical simulations of ship resistance have been performed to compare spatial characteristics of Courant number when using structured and unstructured meshes. When Euler scheme was used for time integration, the structured mesh provided a more efficient calculation because the calculation time interval was larger than that of unstructured mesh. The automatic generation of very small meshes in the unstructured mesh was mainly responsible for the limitation of calculation time interval. When local time stepping Euler scheme was applied, however, the ship resistance of unstructured mesh showed a rapid convergence while a slow convergence of ship resistance in structured mesh was caused by the small time interval in bulbous bow.

Parametric Study on Scouring around Suction Bucket Foundation (파라미터 변화에 따른 석션버켓기초에 발생하는 세굴현상에 대한 수치해석 연구)

  • Park, Sunho;Song, Seongjin;Wang, Haiqing;Joung, Taehwan;Shin, Yunsup
    • Journal of Ocean Engineering and Technology
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    • v.31 no.4
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    • pp.281-287
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    • 2017
  • In the case of fixed offshore wind turbines, scouring phenomena have been reported around sub-structures as a result of currents, which seriously damage the structural stability. A parametric study of the various sub-structures of a fixed offshore wind turbine was performed to investigate their effects on the scouring phenomena. For a suction bucket foundation and monopile, the effects of the stick-up heights and water depth were studied, respectively. The open source libraries, called OpenFOAM, were used to simulate a violent flow around a foundation. The numerical methods were selected based on a two-dimensional analysis of a suction bucket. Based on the results for various stick-up heights, a larger scouring region was observed with an increase in the stick-up height because of the down-wash flow around a foundation. Based on the results for various monopile water depths, the water depth had an insignificant effect on the scouring.

Aerodynamic Simulation of Korea next generation high speed train using open source CFD code (오픈 소스 CFD 코드를 이용한 차세대 고속열차 공력 해석)

  • Kim, B.Y.;Gill, J.H.;Kwon, H.B.
    • 한국전산유체공학회:학술대회논문집
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    • pp.327-330
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    • 2011
  • CFD simulation is widely used in various industries, universities and research centers. In Korea most of the researchers use foreign commercial S/W packages especially in industries. But commercial CFD packages have some problems as limit to source code and very high license foe. So from several years ago open source CFD code has been widely spread as an alternative. But in Korea there are a few users of open source code. Insufficiency of performance validation as for accuracy, robustness, convenience and parallel speed-up is important obstacles of open source code. So we tested some validation cases as to incompressible external aerodynamics and internal flaws and now are doing compressible flaws. As the first stage of compressible flow validation, we simulated Korea next generation high speed train(HEMU). It's running condition is 400km/hr and maximum Mach number reaches up to 0.4. With the high speed train we tested accuracy, robustness and parallel performance of open source CFD code OpenFOAM Because there isn't experimental data we compared results with widely used commercial code. When use $1^{st}$ order upwind scheme aerodynamic forces are very similar to commercial code. But using $2^{nd}$ order upwind scheme there was some discrepancy. The reason of the difference is not clear yet. Mesh manipulation, domain decomposition, post-processing and robustness are satisfactory. Paralle lperformance is similar to commercial code.

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EVALUATION OF OPENFAOM IN TERMS OF THE NUMERICAL PRECISION OF INCOMPRESSIBLE FLOW ANALYSIS (OpenFOAM의 비압축성 유동 해석정밀도 평가)

  • Kim, Hyung Min;Yoon, Dong-Hyeog;Seul, Kwang-Won
    • Journal of computational fluids engineering
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    • v.18 no.2
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    • pp.49-55
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    • 2013
  • The goal of the research is to evaluate the open source code of OpenFOAM for the use of nuclear plant flow simulation objectively. Of the various incompressible flow solvers, simpleFoam, pimpelFoam are then tested under three validated cases (backward facing step, flow over circular cylinder and turbulent round jet flow). For the evaluation of steady state incompressible laminar flow simulation, low reynolds number of backward facing step flow was solved by simpleFoam. The resultant of the reattached lengths turned out to be similar with the other experimental and simulation results. For transient flow simulation, flow over circular cylinder and turbulent round jet flow were solved by pimpleFoam. The simulation accuracy was evaluated by comparing the resultant flow patterns with the description of the characteristics of the flow over the circular cylinder. The quantitative accuracy was evaluated for no more than 85% by comparing it to the decaying constants of the turbulent round jet velocity.

DEVELOPMENT OF OPENFOAM GRID GENERATION PROGRAM FOR TWO-DIMENSIONAL FLOW ANALYSIS (2차원 유동 해석을 위한 OpenFOAM용 격자 생성 프로그램 개발)

  • Kim, W.H.;Kim, B.S.
    • Journal of computational fluids engineering
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    • v.21 no.2
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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.

Analysis on Interaction of Regular Waves and a Circular Column Structure (전산유체역학을 이용한 규칙파와 원형 기둥 구조물의 상호작용 해석)

  • Song, Seongjin;Park, Sunho
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.20 no.2
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    • pp.63-75
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    • 2017
  • In offshore environment, an accurate estimation of a wave-structure interaction has been an important issue for safe and cost effective design of fixed and floating offshore structures exposed to a harsh environment. In this study, a wave-structure interaction around a circular column was investigated with regular waves. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. Wave generation and absorption in the wave tank were activated by the relaxation method, which implemented in a source term. To validate the numerical methods, generated Stokes 2nd-order wave profiles were compared with the analytic solution with deep water condition. From the validation test, grid longitudinal and vertical sizes for wave length and amplitude were selected. The simulated wave run-up and wave loads on the circular column were studied and compared with existing experimental data.

Cryogenic Machining of Open-Cell Silicone Foam (액화질소를 이용한 오픈 셀 실리콘 폼의 냉동 절삭조건 최적화)

  • Hwang, Jihong;Cho, Kwang-Hee;Park, Min-Soo
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.23 no.1
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    • pp.32-37
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    • 2014
  • Open-cell silicon foam is difficult to cut using conventional machining processes because of its low stiffness. That is, open-cell silicon foam is easily pressed down when the tool is engaged, which makes it difficult to remove the material in the form of chip. This study proposes an advanced method of machining open-cell silicon foam by freezing the material using liquid nitrogen. Furthermore, the machining conditions are optimized to maximize the efficiency of material removal and minimize the usage of liquid nitrogen by conducting experiments under various machining conditions. The results show that open-cell silicone foam products with free surface can be successfully machined by employing the proposed method.

Numerical study of the flow smulation and visualization in the co-extrusion die using OpenFOAMⓇ (OpenFOAMⓇ을 이용한 공압출기 다이 내부 유동 모사 및 가시화에 관한 수치 연구)

  • Mun, Jun Ho;Kim, Ju Hyeon;Mun, Sang Ho;Kim, See Jo
    • Journal of the Korean Society of Visualization
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    • v.11 no.3
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    • pp.5-11
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    • 2013
  • It is of great importance to obtain the uniform layer thickness in the multi-layer co-extrusion processes. In the present study, the three-dimensional numerical simulation was carried out using the open source code named OpenFOAM(R) to understand the flow characteristics in the multi-layer die. In this numerical study, Multi-thin-layers were successfully computed depending on the number of repeating units. The generation mechanism for the multi-layer was numerically verified by the flow simulation and visualization in the co-extrusion die using OpenFOAM(R). The results suggested that the multi-layer has a divided and folded mechanism similar to the stretching and folding in the chaotic flow.

A Study on Tools for Control System Platform Vulnerability Scanner Development (제어시스템 플랫폼 취약점 스캐너 도구 개발에 관한 연구)

  • Oh, Kwang-Sun;Ryou, Jae-Cheol
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.202-205
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    • 2016
  • 취약점 스캐너(Vulnerability Scanner)는 이름 그대로 기업의 네트워크나 시스템(컴퓨터, 서버, 라우터 등)을 스캔하고 오픈 포트, 활성화된 IP주소와 로그온, 운영체제, 설치되어 실행되는 소프트웨어와 서비스 등을 식별하고 보고하는 도구이다. 가용성과 데이터의 신뢰성이 우선적으로 중요시되고 있는 제어시스템 환경에서는 이러한 취약점 스캐너 도구의 사용은 운영에 영향을 미칠 수 있다. 본 저자는 기존에 상용화된 스캐너 제품의 취약점 식별 방법을 분석하고 현재까지 발표된 제어시스템 풀랫폼의 공개 취약점 정보를 이용하여 폐쇄적인 제어시스템 운영환경에 적합한 새로운 제어시스템 플랫폼 취약점 스캐너를 제안한다.