• Journal of computational fluids engineering
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• v.12 no.3
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• pp.20-28
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• 2007

A fast and robust method of grid generation to multiple functions has been developed for flow analysis in three dimensional space. It is based on the Non-Uniform Rational B-Spline(NURBS) of an approximation method. Many of NURBS intrinsic properties are introduced and much more easily understood. The grid generation method, details of numerical implementation. examples of application, and potential extensions of the current method are illustrated in this paper. The object of this study is to develop the surface grid generation and the grid cluster techniques capable of resolving complex flows with shock waves, expansion waves, shear layers. The knot insert method of Non-Uniform Rational B-Spline seems well worked. In addition, NURBS has been widely utilized to generate grids in the computational fluid dynamics community. Computational examples associated with practical configurations have shown the utilization of the algorithm.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.310-317
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• 2014

Purpose: This study was conducted to analyze the air flow characteristics in a plant factory with different inlet and outlet locations using computational fluid dynamics (CFD). Methods: In this study, the flow was assumed to be a steady-state, incompressible, and three-dimensional turbulent flow. A realizable k-${\varepsilon}$ turbulent model was applied to show more reasonable results than the standard model. A CFD software was used to perform the numerical simulation. For validation of the simulation model, a prototype plant factory ($5,900mm{\times}2,800mm{\times}2,400mm$) was constructed with two inlets (${\Phi}250mm$) and one outlet ($710mm{\times}290mm$), located on the top side wall. For the simulation model, the average air current speed at the inlet was $5.11m{\cdot}s^{-1}$. Five cases were simulated to predict the airflow pattern in the plant factory with different inlet and outlet locations. Results: The root mean square error of measured and simulated air current speeds was 13%. The error was attributed to the assumptions applied to mathematical modelling and to the magnitude of the air current speed measured at the inlet. However, the measured and predicted airflow distributions of the plant factory exhibited similar patterns. When the inlets were located at the center of the side wall, the average air current speed in the plant factory was increased but the spatial uniformity was lowered. In contrast, if the inlets were located on the ceiling, the average air current speed was lowered but the uniformity was improved. Conclusions: Based on the results of this study, it was concluded that the airflow pattern in the plant factory with multilayer cultivation shelves was greatly affected by the locations of the inlet and the outlet.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.237.2-237.2
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• 2010

Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. The techniques of Computational Fluid Dynamics (CFD) are applied to simulate a wave energy conversion device in free surface such as waves. This research uses the commercially available ANSYS CFX computational fluid dynamics flow solver to model a complete oscillating water column system with savonius turbine incorporated at the rear bottom of the OWC chamber in a three dimensional numerical wave tank. The purpose of the present study is to investigate the effect of an average wave condition on the performance and internal flow of a newly developed direct drive turbine (DDT) model for wave energy conversion numerically. The effects of blade angle and front lip shape on the hydrodynamic efficiency are investigated. The results indicated that the developed models are suitable to analyze the water flow characteristics both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for the all cases. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.

• Journal of ILASS-Korea
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• v.1 no.3
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• pp.37-50
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• 1996

Computational fluid dynamics was used to optimize an A/C duct. Three dimensional flow analysis in an automotive A/C duct was performed computationally using various turbulence models and compared numerical predictions such as outlet flow split, surface pressure distribution along the duct to experimental data. Additionally, we studied the effect of location variation of 2nd branch on exit flow ratio and could find optimal location of 2nd branch. The design of an A/C duct was modeled and calculated to enhance the airflow distribution in each outlet using the STAR-CD computational fluid dynamics software. In results, modified $k-\varepsilon$ turbulence model allows a successful prediction of static pressure distribution particulary at around strong curvature but little improvement flow split. In the future, adoption of CFD to design an A/C duct with modified $k-\varepsilon$ model will bring benefits of producing more accurate prediction, and also give designers more detail information much more than now.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.687-690
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• 2008

Currently, Stream flow analysis has been accomplished by one or two dimensional equations and was applied by simple momentum equations and fixed energy conservations which contain many reach uppermost limit. In this study, FLOW-3D using CFD(Computational Fluid Dynamics) was applied to stream flow analysis which can solve three dimensional RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as $k-\varepsilon$, RNG(Renomalized Group Theory) $k-\varepsilon$ and LES(Large Eddy Simulation). Numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow, water level pressure and eddy flows around the side overflow type structures at Jangwall bridge in urban stream.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1967-1974
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• 2005

The butterfly valve has been used to control a flow effectively in the industrial because of its lightweight, simple structure and the rapidity of its manipulation. However, it is difficult to have the existing structural optimization using field analysis from CFD to structure analysis when the structure is influenced by fluid. This paper is evaluated the specificity to get the flow characteristic and stability of the butterfly valve using FEM and CFD. Also, it accomplished the shape optimization design using the orthogonal arrangement and characteristic function. Research result, a few experiments showed the optimal results of three dimensional structures to be multi-objective.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.473-478
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• 2004

This work presents the Thermal Hydraulic analysis has been performed for a 19-pin wire-spacer fuel assembly using three-dimensional Reynolds-averaged Navier-Stokes equations. SST model is used as a turbulence closure. The whole fuel assembly has been analyzed for one period of the wire-spacer using periodic boundary condition at inlet and outlet of the calculation domain. The overall results far a preliminary calculation show a good agreement with the experimental observations. It has been found that the major unidirectional flows are the axial velocity in sub-channels and the peripheral sweeping flows and the velocities are found to be following a cyclic path of period equal to the wire-wrap pitch. The temperature is found to be maximum in the central region and also, there exist a radial temperature gradient between the fuel rods. The major advantage of performing this kind of analysis is the prediction of thermal-hydraulic behavior of a fuel assembly with much ease.

• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.12-19
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• 2016

In present study, a parametric study of a centrifugal compressor with inlet treatment has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model was used for analysis of turbulence. The finite volume method and unstructured grid system were used for the numerical solution. Tested parameters were related to the geometry of the inlet duct. It was found that the application of circumferentially distributed holes in the inlet duct improves operational stability of the compressor compared to that with conventional inlet duct.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.29-34
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• 2010

In this paper, aerodynamic noise of axial flow fans for outdoor unit of air-conditioner was analyzed by both experiment and numerical simulation. The three-dimensional incompressible turbulent flow was predicted by the commercial computational fluid dynamics code SC/Tetra, while the aeroacoustic noise of an axial flow fan was predicted by FlowNoise. Computations and experiments were performed with two types of axial flow fans, in which very different noise source distributions were presented. The results obtained from this study are expected to show the way to reduce the noise of axial flow fans in industrial applications.