• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.72-80
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• 2018

With the ever increasing advances in computers and their computing power, computational fluid dynamics(CFD) has become an essential engineering tool in the design and analysis of engineering applications. Accordingly, many universities have developed and implemented a course on CFD for undergraduate students. On the other hand, many professors have used industrial examples supplied by computational analysis software companies as CFD examples. This makes many students think of CFD as difficult and confusing. This paper presents a simple CFD example used in the department of mechanical design engineering of Kangwon National University and shows its effectiveness. Most students answered that a simple CFD example is more comprehensive than an industrial example. Therefore, it is necessary to develop simple computational analysis problems in the engineering education field.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.224-229
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• 2004

The objective of this work is not only to perform feasibility studies on the CFD (computational fluid dynamics) analysis for the capillary system design but also to provide an enhanced understanding of the autonomous capillary flow. The capillary flow is evaluated by means of the commercial CFD software of FLUENT, which includes the VOF (volume-of-fluid) model for multiphase flow analysis. The effect of wall adhesion at fluid interfaces in contact with rigid boundaries is considered in terms of static contact angle. Feasibility studies are first performed, including mesh-resolution influence on pressure profile, which has a sudden increase at the liquid/gas interface. Then we perform both 2D and 3D simulations and examine the transient nature of the capillary flow. Analytical solutions are also derived for simple cases and compared with numerical results. Through this work, essential information on the capillary system design is brought out. Our efforts and initial success in numerical description of the microfluidic capillary flows enhance the fundamental understanding of the autonomous capillary flow and will eventually pave the road for full-scale, computer-aided design of microfluidic networks.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.121-130
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• 2021

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.3
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• pp.167-174
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• 2013

Model ice forming process in ice tank needs several steps of seeding, freezing, tempering. In those process, one of the most important factors to affect the accuracy of experiment is the homogeneity of the ice thickness and the temperature. This paper investigated a computational and statistical method to assess the uniformity of the model ice. In addition, the different configurations of freezing systems were considered to improve the uniformity. Qualitative assessment using streamlines from the cooling units was carried out by computational fluid dynamics (CFD) and the quantitative evaluations of the homogeneity were compared using the temperature distribution on the ice surface. In addition, multi species transport analysis is introduced to understand the circulation efficiency of cold air from the cooling units. As the results, optimized configurations were determined by adjusting the angles of vane in the cooling units.

• Wind and Structures
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• v.17 no.4
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• pp.361-377
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• 2013

Wall functions have been widely used in computational fluid dynamics (CFD) simulations and can save significant computational costs compared to other near-wall flow treatment strategies. However, most of the existing wall functions were based on the asymptotic characteristics of near-wall flow quantities, which are inapplicable in complex and non-equilibrium flows. A modified wall function is thus derived in this study based on flow over a plate at zero-pressure gradient, instead of on the basis of asymptotic formulations. Turbulent kinetic energy generation ($G_P$), dissipation rate (${\varepsilon}$) and shear stress (${\tau}_{\omega}$) are composed together as the near-wall expressions. Performances of the modified wall function combined with the nonlinear realizable k-${\varepsilon}$ turbulence model are investigated in homogeneous equilibrium atmosphere boundary layer (ABL) and flow around a 6 m cube. The computational results and associated comparisons to available full-scale measurements show a clear improvement over the standard wall function, especially in reproducing the boundary layer flow. It is demonstrated through the two case studies that the modified wall function is indeed adaptive and can yield accurate prediction results, in spite of its simplicity.

• Wind and Structures
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• v.37 no.4
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• pp.255-274
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• 2023

The aim of this paper is to enhance the accuracy of predicting time-averaged external surface pressures on low-rise buildings by utilizing Computational Fluid Dynamics (CFD) simulations. To achieve this, benchmark studies of the Silsoe cube and the Texas Tech University (TTU) experimental building are employed for comparison with simulation results. The paper is structured into three main sections. In the initial part, an appropriate domain size is selected based on the precision of mean pressure coefficients on the windward face of the cube, utilizing Reynolds Averaged Navier-Stokes (RANS) turbulence models. Subsequently, recommendations regarding the optimal computational domain size for an isolated building are provided based on revised findings. Moving on to the second part, the Silsoe cube model is examined within a horizontally homogeneous computational domain using more accurate turbulence models, such as Large Eddy Simulation (LES) and hybrid RANS-LES models. For computational efficiency, transient simulation settings are employed, building upon previous studies by the authors at the Windstorm Impact, Science, and Engineering (WISE) Lab, Louisiana State University (LSU). An optimal meshing strategy is determined for LES based on a grid convergence study. Three hybrid RANS-LES cases are investigated to achieve desired enhancements in the distribution of mean pressure coefficients on the Silsoe cube. In the final part, a 1:10 scale model of the TTU building is studied, incorporating the insights gained from the second part. The generated flow characteristics, including vertical profiles of mean velocity, turbulence intensity, and velocity spectra (small and large eddies), exhibit good agreement with full-scale (TTU) measurements. The results indicate promising roof pressures achieved through the careful consideration of meshing strategy, time step, domain size, inflow turbulence, near-wall treatment, and turbulence models. Moreover, this paper demonstrates an improvement in mean roof pressures compared to other state-of-the-art studies, thus highlighting the significance of CFD simulations in building aerodynamics.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.579-584
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• 2008

The importance and the interest of wind load have emphasized since the damage of the Jeju World cup Stadium and Main Stadium of Busan Asiad in 2002, and the appearance of high-rise buildings. In general, a evaluation for the wind load acting on structures have been carried out mainly through the wind tunnel test, but this technique has the huge shortcomings that consume too much cost and experimental time. However, with the rapid advances on computers, it is possible to analyze the wind pressure distribution acting on structures by numerical scheme. In this paper, to predict the wind pressure distribution acting on shell structures having the various shape by numerical simulation, governing equations of fluid flow and turbulent model is formulated. Also, evaluates the wind pressure coefficient in accordance with the structural shape for shell structures like as a membrane structures and dome structures.

• New & Renewable Energy
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• v.3 no.3
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• pp.54-62
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• 2007

The present paper describes the scale effect correction methods for scaled NREL Phase VI wind turbines by using CFD[computational fluid dynamics). For the corrections of wind turbine scale effect, various researches on the helicopter rotor scale effect were investigated and the feasibility study of the methods was performed to correct wind turbine scale effect. The present paper also introduces scale effect correction methods based on two dimensional lift slope. In order to test the present method, performance analyses of NREL Phase VI wind turbines under various scale conditions were carried out and new correction method was applied. Granting that the new correction method is valid only above Reynolds No. 100,000, it showed reasonable agreement between model and full scale wind turbines in the linear torque region.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.456-463
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• 1997

Atrium buildings are commonly found in Hong Kong since 1980. Those spaces are usually crowded with people and so fire protection systems have to be installed for providing a safe environment. Smoke control system was identified to be important but no clear design guidelines are available because the smoke filling process was not well-understood. In this paper., Computational Fluid Dynamics(CFD) or fire field model is applied to study the smoke filling pattern in atrium. Two common cases on smoke spreading out from a shop adjacent to the atrium; and with a fire located at the atrium floor itself were considered. Simulations with a modified form of the CFD package TEAM were performed. Application of the predicted results Is illustrated.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.76-85
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• 2023

The present study aims to review the wave pattern resistance analysis method suggested by the International Towing Tank Conference. From the experimental database of a container carrier ship model, the wave pattern measurement and resistance test results are utilized. The wave pattern resistance at the design Froude number is obtained to be compared with the wave making resistance of experiments. Wave pattern resistance is lower than wave making resistance by 1978 ITTC and uniform regardless of transverse location of wave cut. The method is also applied to the wave height field by Computational Fluid Dynamics (CFD) analyses with Froude number variation. Although numerical damping suppressed waves in downstream, waves around the hull and wave pattern resistance are properly predicted.