• Title, Summary, Keyword: 오픈폼

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Regular Wave Generation Using Three Different Numerical Models under Perfect Reflection Condition and Validation with Experimental Data (세 가지 수치모델을 이용한 완전반사 조건에서의 규칙파 조파 및 수리실험 검증)

  • Oh, Sang-Ho;Ahn, Sukjin
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.31 no.4
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    • pp.199-208
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    • 2019
  • Regular waves were generated in a wave flume under perfect reflection condition to evaluate performance of three CFD models of CADMAS-SURF, olaFlow, and KIOSTFOAM. The experiments and numerical simulations were carried out for three different conditions of non-breaking, breaking of standing waves, and breaking of incident waves. Among the three CFD models, KIOSTFOAM showed best performance in reproducing the experimental results. Although the run time was reduced by using CADMAS-SURF, its computational accuracy was worse than KIOSTFOAM. olaFlow was the fastest model, but active wave absorption at the wave generation boundary was not satisfactory. In addition, the model excessively dissipated wave energy when wave breaking occurred.

Prediction of Resistance and Planing Attitude for Prismatic Planing Hull using OpenFOAM (OpenFOAM을 이용한 주형체 활주선의 저항 및 항주자세 추정)

  • Shi, XiangYu;Zhang, Yang;Yum, Deuk-joon
    • Journal of Ocean Engineering and Technology
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    • v.33 no.4
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    • pp.313-321
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    • 2019
  • The prediction of the hydrodynamic performance of a planing hull vessel is an important and challenging topic for computational fluid dynamic (CFD) applications to naval hydrodynamics. In this paper, the resistance and planing attitude analysis for a Fridsma hull, which is a prismatic planing hull, in still water are numerically studied using OpenFOAM. OpenFOAM is an open source code package based on C++ libraries and the finite volume method (FVM) for the discretization of the RANS equation. The volume of fluid method (VOF) is used to capture the water-air interface and the SST ${\kappa}-{\omega}$ model is used for the turbulence simulation. The overset mesh method is used to capture the large motion of the hull at higher speeds. Before the extensive analysis, uncertainty analyses using various time steps and grid sizes were performed for one ship speed case of Fn = 1.19. The results of the present study are compared with those of a model test, other CFD research, and Savitsky's empirical formula. The results of the present study, following the trend of other CFD results, slightly over predict the resistance and under predict the sinkage and, more significantly, the trim.

A Parametric Study on EOM-based 2D Numerical Wave Generation using OpenFOAM (OpenFOAM을 이용한 EOM 기반 2차원 수치 파 생성에 관한 파라메트릭 연구)

  • Moon, Seong-Ho;Lee, Sungwook;Paik, Kwang-Jun;Kwon, Chang-Seop
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.6
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    • pp.490-496
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    • 2018
  • The consistency of the initially designed waves in the domain is essential for accurate calculation of the added resistance in waves through CFD. In particular, unwanted reflected waves at domain boundaries can cause incorrect numerical solutions due to the superposition with initially designed waves. Euler Overlay Method(EOM) is one of the methods for reducing wave reflections by adding an additional source term to momentum and phase conservation equations, respectively. In this study, we apply the Euler Overlay Method(EOM) to the open-source CFD library, OpenFOAM(R), to simulate the accurate free-surface waves in the domain and the parametric study is performed for efficient implementation of Euler Overlay Method(EOM). Considering that the damping efficiency depends on the selection of the overlay parameter in the added source terms, the size of overlay zone and the wave steepness, the influences of these factors are tested through the wave elevation measured at constant time intervals in the 2D numerical wave tank. Through this process, guidelines for selection of optimal overlay parameter and overlay zone size that can be applied according to the scaling law are finally presented.

Effect of Gas Channel/Rib Width in Solid Oxide Fuel Cells (고체산화물 연료전지에서 가스채널/리브 폭의 영향에 관한 연구)

  • Jeon, Dong Hyup;Shin, Dong-Ryul;Ryu, Kwang-Hyun;Song, Rak-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.2
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    • pp.109-115
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    • 2017
  • Using the computational fluid dynamics (CFD) technique, we performed a numerical simulation in anodesupported solid oxide fuel cell (SOFC). The effect of gas channel/rib width on the cell performance and temperature uniformity was investigated in planar type SOFC. The open source CFD toolbox, OpenFOAM, was used as a numerical analysis tool. As a result, the effect of gas channel/rib width on the cell performance and temperature uniformity was not significant if the oxygen depletion is not occurring. On the other hand, the usage of a wide rib and operation at high current density may lead to performance degradation due to oxygen depletion.

Development of quasi-static analysis program for catenary mooring system using OpenFOAM (OpenFOAM을 이용한 catenary 계류시스템의 준정적 해석 프로그램 개발)

  • Choi, Jun Hyeok;Lee, Seung Jae
    • Journal of Ocean Engineering and Technology
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    • v.31 no.4
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    • pp.274-280
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    • 2017
  • Generally, global performance analysis in offshore platforms is performed using potential-based numerical tools, which neglect hydrodynamic viscous effects. In comparison with the potential theory, computational fluid dynamics (CFD) methods can take into account the viscous effects by solving the Navier-Stokes equation using the finite-volume method. The open-source field operation and manipulation (OpenFOAM) C++ libraries are employed for a finite volume method (FVM) numerical analysis. In this study, in order to apply CFD to the global performance analysis of a hull-mooring coupled system, we developed a numerical wave basin to analyze the global performance problem of a floating body with a catenary mooring system under regular wave conditions. The mooring system was modeled using a catenary equation and solved in a quasi-static condition, which excluded the dynamics of the mooring lines such as the inertia and drag effects. To demonstrate the capability of the numerical basin, the global performance of a barge with four mooring lines was simulated under regular wave conditions. The simulation results were compared to the analysis results from a commercial mooring analysis program, Orcaflex. The comparison included the motion of the barge, catenary shape, and tension in the mooring lines. The study found good agreement between the results from the developed CFD-based numerical calculation and commercial software.

The Performance Estimation of Rotor in Wind Fence by Rotor Analysis Solver based on Actuator Disk Model (Actuator Disk Model 기반의 로터 해석자를 사용한 방풍 구조물 내부의 로터 성능 예측)

  • Kim, Taewoo;Oh, Sejong;Kang, Hee Jung;Yee, Kwanjung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.6
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    • pp.429-439
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    • 2013
  • The purpose of current study is to develop the rotor analysis solver and perform a rotor aerodynamic analysis in the wind fence. To this end, the rotor analysis solver based on actuator disk model was employed. To consider the asymmetric effect of the rotor in the wind fence, the flapping motion analysis was conducted with blade element theory for the effective angle of attack calculation. The validation cases which are the rotor with wall and ground were accomplished by developed solver. The decrease of rotor performance by wind fence was confirmed. The wind fence configuration was suggested which guarantees more than 95% rotor performance compared with the no fence case.

DEVELOPMENT OF 2ND GENERATION ICE ACCRETION ANALYSIS PROGRAM FOR HANDLING GENERAL 3-D GEOMETRIES (3차원 착빙 형상 예측을 위한 2세대 시뮬레이션 코드 개발)

  • Son, Chankyu;Oh, Sejong;Yee, Kwanjung
    • Journal of computational fluids engineering
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    • v.20 no.2
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    • pp.23-36
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    • 2015
  • The $2^{nd}$ generation ice accretion analysis program has been developed and validated for various icing conditions. The essential feature of the $2^{nd}$ generation code lies in its capability of handling general 3-D geometry and improved accuracy. The entire velocity fields are obtained based on Navier-Stokes equations in order to take the massively separated flow field into account. Unlike $1^{st}$ generation code, the droplet trajectories are calculated using Eulerian approach, which is adopted to yield appropriate collection efficiency even in the shadow region. For improved thermodynamic analysis on the surfaces, water film model and modified Messinger model are newly included in the present analysis. The ice shape for a given time step is obtained by considering the exact amount of ice accreted on the surface. Each module of the icing analysis code has been seamlessly integrated on the OpenFOAM platform. The developed code was validated against available experimental data for 2D airfoils and 3D DLR-F4. Due to the lack of experimental data, the computed results of DLR-F4 were compared with those obtained from FENSAP-ICE, which is state-of-the-art 3D icing analysis code. It was clearly shown that the present code produces comparable results to those of FENSAP-ICE, in terms of prediction accuracy and the capability of handling general 3-D geometries.

NUMERICAL SIMULATION ON CONTROL OF HUMIDITY AND AIR TEMPERATURE IN THE GRADIENT BIOME (환경경도 바이옴 내의 온도 및 습도 제어 시뮬레이션)

  • Jeong, S.M.
    • Journal of computational fluids engineering
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    • v.21 no.2
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    • pp.32-39
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    • 2016
  • The Gradient Biome is a unique and large greenhouse(length 200 m, width 50 m, height:40 m) in which the elements of the weather, such as temperature and humidity, are controlled and reproduced in such a way as to create a continuous gradient from the tropical to frigid zones along specified longitudinal or transvers lines on the earth. One of the main purposes of the Gradient Biome is to observe the possible responses of the ecosystems (mainly plants), which are to be corresponding to each test climate and be introduced in the Biome, to the expected global warming. As one of the expected responses is the shift of the ecosystem(s) toward the region of suitable environment, there should be no artificial obstacles, which can prevent the shift, inside the facility. However, it is important but not so easy to find the ways of how the temperature and humidity in the Biome could be reproduced since the environmental variables tends to be homogeneous. In this paper, numerical simulations were carried out to find the effective control methods for air temperature and humidity inside the real scale Biome. One of the contributed solvers of OpenFOAM, which is an open source physics simulation code, was modified and used for the simulations.

Numerical Analysis on Aerodynamic Performances and Characteristics of Quad Tilt Rotor during Forward Flight (전진 비행하는 쿼드 틸트 로터의 공력성능 및 특징에 대한 수치적 연구)

  • Lee, Seonggi;Oh, Sejong;Choi, Seongwook;Lee, Yunggyo;Park, Donghun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.3
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    • pp.197-209
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    • 2018
  • In this study, numerical analyses on Quad Tilt Rotor(QTR) are carried out to investigate the interference effect of components and effect of operating condition during forward flight. Actuator Surface Method(ASM) which is implemented in an open source CFD code, OpenFOAM, is used to calculate the flow field around QTR with high computational efficiency. The lift of the front and rear wing is found to increase or decrease depending on the rotation direction of the rotor. At the rear wing, the interference effects of the front and rear rotor appear as a combined manner. Performance change due to the phase difference is found to be insignificant. For both rotors, the locally higher thrust is generated by the blockage effect of the wing. The interference effect of wake from the front nacelle contributes to higher local thrust for the rear rotor compared to the front rotor. And it is observed that the amplitude of thrust oscillation can decrease depending on the phase difference between the rotors. Aerodynamic performances of both rotors and the entire aircraft were compared and analyzed for various operating conditions.

Physical Properties of Reticulated Polyurethane Foams and the Enhancement of Microbial Adhesion through their Surface Treatments (망상 폴리우레탄 폼의 물성 및 표면처리를 통한 미생물 고정화 특성의 향상)

  • 김시욱;장영미;명성운;최호석
    • KSBB Journal
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    • v.18 no.5
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    • pp.412-417
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    • 2003
  • We first investigated basic characteristics of reticulated polyurethane (PU) foams as microbial carriers. In general, the specific surface area of PU foams increases with respect to decreasing pore sizes. However, the number of microbes adhered on the unit surface of reticulated PU foams decreases with respect to decreasing pore sizes. Thus, as a result of totally considering all effects such as apparent density, hydrolysis rate, and adhesion, we can know that PU foams with 45 PPI is the most appropriate microbial carrier. In this study, we can also investigate the effect of various physico-chemical surface treatments on the adhesion of microbes on the surface of PU foams. We used a chitosan treatment, a PEI (Polyethylene Imine) treatment, a xanthane treatment and a plasma treatment. As a result of comparing all surface treatments, the plasma surface treatment was the best.