• Journal of Advanced Research in Ocean Engineering
• /
• 제1권1호
• /
• pp.14-24
• /
• 2015

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.

• International Journal of Ocean System Engineering
• /
• 제4권1호
• /
• pp.49-56
• /
• 2014

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권3호
• /
• pp.540-558
• /
• 2015

Maneuvering oblique towing test is simulated in a Computational Fluid Dynamic (CFD) environment to obtain the linear and nonlinear velocity dependent damping coefficients for a DTMB 5512 model ship. The simulations are carried out in freely accessible OpenFOAM library with three different solvers, rasInterFoam, LTSInterFoam and interDyMFoam, and two turbulence models, $k-{\varepsilon}$ and SST $k-{\omega}$ in presence of free surface. Turning and zig-zag maneuvers are simulated for the DTMB 5512 model ship using the calculated damping coefficients with CFD. The comparison of simulated results with the available experimental shows a very good agreement among them.

• 대한기계학회논문집B
• /
• 제29권1호
• /
• pp.151-158
• /
• 2005

A characteristic of discharge for a foam spray nozzle with various parameters was investigated. The discharge patterns from a fire foam spray nozzle are important to evenly spray over a maximum possible floor area. Two parameters of a foam spray nozzle were chosen, and compared with those from the standard one. Also, in order to evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-protection foams were experimentally investigated. A simple repeatable test for fire-protection foams subjected to fire radiation was developed. This test involves foam generation equipment, a fire source for heat generation, and data acquisition techniques. Results show that the bubble size of foam is increased by large inside diameter of orifice or closed air hole, but phenomenon of discharge angle and expansion ratio is opposite. For the case of the open air hole, liquid film of a circular cone discharges with formation, growth, split and fine grain. In case of the closed air hole, a pillar of foam solution discharges with that. Though the temperature gradient in the foam increases with increased foam expansion ratio. it is not change with increased intensity of heat flux.

• 한국해양공학회지
• /
• 제31권4호
• /
• pp.274-280
• /
• 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.

• 대한기계학회논문집B
• /
• 제41권2호
• /
• pp.135-143
• /
• 2017

밀폐된 공간내의 공조 문제에 있어서 실내의 기류 및 온도 특성을 전산유체역학기법을 통해 쉽게 예측할 수 있는 맞춤형 시뮬레이터를 개발하였다. 본 시스템에서는 사용자가 직접 해석 대상 평면도를 입력하고 적절한 경계조건을 설정하면 전산유동해석을 위한 계산 격자가 자동으로 생성되고 유한체적법으로 이산화된 공개 전산유체코드를 통해 주어진 공간내의 열유체 해석 결과를 얻게 된다. 초기 실내 평면도면 입력부터 경계조건 설정, 전산유동해석 결과까지 하나의 사용자 인터페이스 상에서 작업할 수 있으며 격자생성과 유동해석 알고리듬은 공개 라이브러리를 사용하여 구현하였다. 간단한 실험 데이터를 통해 해석결과를 검증하였으며 실제 실내 공조에 대한 기류해석을 통해 유동의 경향성을 파악할 수 있는 맞춤형 유동전산모사 시스템을 구성하였다.

• 대한조선학회논문집
• /
• 제55권6호
• /
• pp.490-496
• /
• 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.

• 농업과학연구
• /
• 제10권2호
• /
• pp.345-353
• /
• 1983

수용액에 존재하는 중금속이온중의 Hg(II)을 정량적으로 분리 회수하기 위하여 DBHQ(5. 7-dibromo-8-hydroxyquinoline)을 Open-pore polyurethane foam (OPP foam)에 침윤시켜 수지의 응용성을 연구하였다. Hg(II)의 흡착은 DBHQ와 1:2 몰비의 착물형성이 이루어지며 Hg(II)의 흡착과 분리는 Batch법으로 실험하여 최적조건을 결정하였다. 가장 양호한 흡착은 DBHQ의 등전점인 pH5.0 부근에서 그리고 분리하는데는 4M-HCl, 50% 아세톤 용매를 사용하였을 경우가 비교적 정량적인 흡착과 분리가 이루어지는 조건이었으며 이와같은 결과를 기초로 DBHQ-OPP foam에 대한 Hg(II)의 흡착 및 분리에 대한 반응메카니즘을 제안했다.

• Nuclear Engineering and Technology
• /
• 제56권2호
• /
• pp.611-623
• /
• 2024

The ISP-47 TOSQAN experiment was analyzed with containmentFOAM which is an open-source CFD code based on OpenFOAM. The containment phenomena taking place during the experiment are gas mixing, stratification and wall condensation in a mixture composed of steam and non-condensable gas. The k-ω SST turbulence model was adopted with buoyancy turbulence models. The wall condensation model used is based on the diffusion layer approach. We have simulated the full TOSQAN experiment which had a duration 20000 s. Sensitivity studies were conducted for the buoyancy turbulence models with SGDH and GGDH and there were not significant differences. All the main features of the experiments namely pressure history, temperature, velocity and gas species evolution were well predicted by containemntFOAM. The simulation results confirmed the formation of two large flow stream circulations and a mixing zone resulting by the combined effects of the condensation flow and natural convection flow. It was found that the natural convection in lower region of the vessel devotes to maintain two large circulations and to be varied the height of the mixing zone as result of sensitivity analysis of non-condensing wall temperature. The computational results obtained with the 2D mesh grid approach were comparable to the experimental results.

• 대한조선학회논문집
• /
• 제53권4호
• /
• pp.329-335
• /
• 2016

In the present paper, Computational fluid dynamics (CFD) uncertainty analysis proposed by ITTC was investigated and applied to ship resistance performance using open source libraries, called OpenFOAM. Uncertainties for grid size, time step and iteration number were studied. Wave patterns and hull wave profile were compared for various uncertainty parameters. From results, grid size uncertainty was mainly contributed to simulation numerical uncertainty.