• Journal of the Society of Naval Architects of Korea
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• v.53 no.4
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• pp.329-335
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• 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.155-162
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• 2015

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value. However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier-Stokes equations combined with a $k-{\varepsilon}$ turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.99-112
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• 2021

The prediction of maneuverability is very important in the design process of an underwater vehicle. In this study, we predicted the steady turning ability of a symmetrical underwater vehicle while considering interactions between the yaw rate and drift/rudder angle through a simulation-based methodology. First, the hydrodynamic force and moment, including coupled derivatives, were obtained by computational fluid dynamics (CFD) simulations. The feasibility of CFD results were verified by comparing static drift/rudder simulations to vertical planar motion mechanism (VPMM) tests. Turning motion simulations were then performed by solving 2-degree-of-freedom (DOF) equations with CFD data. The turning radius, drift angle, advance, and tactical diameter were calculated. The results show good agreement with sea trial data and the effects on the turning characteristics of coupled interaction terms, especially between the yaw rate and drift angle.

• Journal of Korean Association for Spatial Structures
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• v.21 no.1
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• pp.51-59
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• 2021

In this paper, the effect of the turbulence intensity in across-wind direction on the wind load in CFD(Computational fluid dynamics) simulation was analyzed. 'Ansys fluent' software was used for CFD simulation. And the fluctuating wind speed applied to the simulation was generated according to Korean Design Standard and Von Karman wind turbulence model. The turbulence intensity in across-wind direction for simulation was applied from 0 to 100% of the turbulence intensity in along-wind direction. The analysis results showed that the turbulence intensity in across-wind direction had a particularly great effect on the wind load in across-wind direction.

• Wind and Structures
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• v.34 no.3
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• pp.259-274
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• 2022

The present paper is focused on analyzing a set of Computational Fluid Dynamics (CFD) simulation data on reducing orthogonal peak base moment coefficients on a high-rise rectangular building with wings. The study adopts an aerodynamic optimization procedure (AOP) composed of CFD, artificial neural network (ANN), and genetic algorithm (G.A.). A parametric study is primarily accomplished by altering the wing positions with 3D transient CFD analysis using k - ε turbulence models. The CFD technique is validated by taking up a wind tunnel test. The required design parameters are obtained at each design point and used for training ANN. The trained ANN models are used as surrogates to conduct optimization studies using G.A. Two single-objective optimizations are performed to minimize the peak base moment coefficients in the individual directions. An additional multiobjective optimization is implemented with the motivation of diminishing the two orthogonal peak base moments concurrently. Pareto-optimal solutions specifying the preferred building shapes are offered.

• Design & Manufacturing
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• v.13 no.3
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• pp.41-47
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• 2019

In conventional machining, the use of cutting fluid is essential to reduce cutting heat and to improve machining quality. However, to increase the performance of cutting fluids, various chemical components have been added. However, these chemical components during machining have a negative impact on the health of workers and cutting environment. In current machining, environment-friendly machining is conducted using MQL (minimum quantity lubrication) or cryogenic air spraying to minimize the harmful effects. In this study, the injection nozzle that can combined injecting minimum quantity lubrication(MQL) and cryogenic gas was designed and the shape optimization was performed by using computational fluid dynamics(CFD) and design of experiment(DOE). Performance verification was performed for the designed nozzle. The diameter of the sprayed fluid at a distance of 30 mm from the nozzle was analyzed to be 21 mm. It was also analyzed to lower the aerosol temperature to about 260~270K.

• KIEAE Journal
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• v.10 no.2
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• pp.63-69
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• 2010

Diverse problems in wind environment has occurred through rapid urbanization and growth of high-rise building numbers, This study aims to propose the CFD (Computational Fluid Dynamics) simulation method and evaluation standard of wind environment in site planning of high rise apartment housing. The CFD simulation method proposed in this study is not existing detail simulation, but it is the method that a designer can correct and develop the design through immediate evaluation of design options in concept design phase. Therefore, the proposed CFD simulation method of wind environment in this study uses the BIM based CFD tool in which the 3D model in concept design phase can be used as for the CFD simulation. In this paper, the study examines existing evaluation standards of comfortableness level in wind environment for pedestrian near buildings, and selects new evaluation method which is possible to apply to the proposed CFD simulation method. In addition, it is to examine calculation time-spending and appropriate mesh division method for finding CFD result which is useful to find the best design options in aspect of wind environment in concept design phase. Furthermore, it proposes the wind environment evaluation method through BIM based CFD simulation.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.58-65
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• 2012

Various models are currently applied to predict the dispersion of leaked combustible gas and overpressure from a vapor cloud explosion(VCE). However, those models use simple approaches where topography and barriers of anti-leakage facilities and the effects of buildings were not sufficiently taken into considerations. For this reason, this study has proposed the dispersion process of leaked gas, distribution patterns, and flames and overpressure generated from gas explosions in 2D and 3D virtual spaces by reviewing more accurately analyzable computational fluid dynamics (CFD) model by considering various variables including combustion types of leaked substances, geometry of facility, warm currents, barriers, the influence of wind, and others. The CFD analysis results are anticipated to be usefully applied for the risk analysis of explosion and for the risk-based design.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1080-1087
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• 2019

For a risk analysis in a chemical process, it is important to reflect correctly the characteristic properties of the target process. In this study, computational fluid dynamics (CFD) was adopted for the advanced risk analysis in a residual hydro desulfurization (RHDS) process by considering operation condition, layout of instruments and facilities, atmospheric condition, and wind direction. Release and explosion simulations for the RHDS by using FEA (Finite Element Analysis) and CFD showed the applicability of 3D scanning methods for estimation of release hole size and release amount.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.1-6
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• 2015

In this study, a numerical prediction on propulsive performance of a ducted propeller in open water condition was carried out by solving Reynolds averaged Navier-Stokes(RANS) equation using computational fluid dynamics(CFD). A configuration of propeller Ka-470 inside duct 19A was considered. Hexahedral grid system was generated by dividing whole computational domain into three separate regions; propeller, duct and outer flow region. A commercial CFD software, ANSYS-CFX was used for numerical simulations. Results were compared with experimental data and showed considerable improvement in accuracy, in comparison to those from surface panel method which is based on potential flow assumption. The results also exhibited the importance of grid system within the gap between the inner surface of duct and blade tip for accurate prediction of propulsive performance of ducted propeller.