• Journal of computational fluids engineering
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• v.3 no.1
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• pp.11-21
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• 1998

A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity now: (ⅰ) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ⅱ) driven only by uniform shear (of the classical type).

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.11-16
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• 2001

It is not easy to apply a small-sized centrifugal fan to the duct used for the thermal management of home electronic appliances due to complex design parameters of its blades and scroll. The main objective of this study was to develop the systematic process to design an optimal centrifugal fan based on the 3-dimensional configuration of blades obtained from the conceptual design program self-developed with the given design constraints such as the flow rate, the total pressure loss, the size of fan, and the number of rotation. The design process to find an optimal centrifugal fan for refrigerator was technologically linked in many ways. The complex grid generation system of the fan model included scroll was adopted for the numerical simulation. The FVM CFD code, FLUENT, was used to investigate the three dimensional flow pattern at the coordinate system of rotating frame and to check the optimal performance of the fan. By using this design process, a selected centrifugal fan was designed, numerically simulated, manufactured and experimentally tested in the wind tunnel. The performance curve of fan manufactured by NC process was compared with numerically obtained characteristic curve. The developed design method was proved into being excellent because these two curves were well matched.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3686-3694
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• 1996

A numerical investigation of natural convection flow along irregular vertical surfaces is reported. A transformation method is applied to the problem of natural convection under the assumption of a large Grashof number. A vertical wavy surface is used as an example to demonstrate the advantages of the transformation method, and to show the heat transfer mechanism near such surfaces. Surface non-uniformities on the boundary layer flow induced by a constant was temperature, semi-infinite surface are investigated. Also the effects of Prandtl number, flow index, and surface amplitude in Non-Newtonian fluids are discussed. When possible, the comparison of the numerical results shows a good agreement. The amplitude is proportional to the amplitude of a wavy surface. The results demonstrate that the local heat flux along a wavy surface is smaller than that of a flat surface. The frequency of the wavy surface is half that of the local heat transfer rate. The amplitude of the local Nusselt number gradually decreases downstream where the natural convection boundary layer grows thick.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.946-953
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• 2012

When water shortage has been getting worse recently, toilet water-saving is one of the most effective way to solve the water shortage. Therefore, in this study, toilet flushing performance was investigated with VOF(Volume Of Fluid) model to obtain the basic design data for the development of high-efficiency toilets. The result showed that the shorter trapway, the longer the flushing duration time. However, the shorter trapway is found to have disadvantage in exhausting dirt due to relatively weak siphon and higher curvature. Since the remaining water in a trapway appears to help siphon, it is also an important factor in developing high-efficiency toilets. Although higher water level in the water tank shows better performance in flushing, lower water level is preferred to save water. Too low water level may cause dirt to clog the trapway due to relatively weak siphon.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.9-16
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• 2000

This paper deals with the numerical and experimental study on the characteristics of the flow around a sunken vessel. Numerical simulation of the two dimensional steady flow on the midship section are carried out by the CFD code which is developed by using finite volume method and which includes the standard $textsc{k}$-$\varepsilon$ model with standard wall function. A experimental study is also carried out for the 1/100 scale model in circulating water channel. A velocity fields around the ship are measuremed by using particle image velocimetry technique. And the fluid forces acting on the ship hull by uniform current are measured by two axis load cell. The computed and measured velocity fields on the midship section are compared with each other in the view point of velocity dstribution and reattachement length, which shows good agreement in quality. The drag force on the vessel also showed the same tendency in both computational and experimental results. However, the quantitative disagreements are shown due to the three dimensional effect of the experiment. The result are used to determine the functional efficiency and stability of the vessel as a artificial reef.

• Journal of the Mineralogical Society of Korea
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• v.19 no.3 s.49
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• pp.189-195
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• 2006

Compression work on a pyrite powder has been carried out using energy dispersive X-ray diffraction (EDXRD) with Mao-Bell type diamond anvil cell (DAC) and synchrotron radiation(SR) at room temperature. It has been reported the bulk moduli of pyrite show the large variations depending on the experimental conditions as well as the apparatus used. Thus, two kinds of sample in different pressure transmitting media of both NaCl and MgO powder emerged in alcoholic fluids were subjected to measure their compressibilities. Bulk moduli thus obtained are 138.9 GPa and 198.2 GPa, respectively, and this result contradicts to the anticipated values according to the hydrostaticity conditions of the sample chamber. This might be due to the alcoholic fluids phase transition mainly with the side effects from the difference of both solid state detector (SSD) used and E*d value applied. All experiments were performed at the Beam Line 1B2 of Pohang Light Source (PLS).

• Journal of the Korea Computer Graphics Society
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• v.15 no.1
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• pp.1-6
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• 2009

This paper presents a new CIP method for unstructured mesh to reduce the numerical dissipation. To reflect precise physical characteristics, CIP method updates both the physical quantity and the derivative information. The proposed method uses the Finite Volume Method(FVM) to solve the non-advection term of CIP equation. And we performed several experiments to improve the accuracy of third-order interpolation. Our result shows that our algorithm has less numerical dissipation than that of linear advection solver.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.135-143
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• 2017

A customized CFD simulator to perform thermo-fluid dynamic simulations of an HVAC for an indoor space is presented. This simulation system has been developed for engineers studying architectural engineering, as the HVAC mechanical systems used in housings and buildings. Hence, all functions and options are so designed to be suitable that they are suitable for non-CFD experts as well as CFD engineers. A Computational mesh is generated by open-source libraries, FEMM (Finite Element Method Magnetics), and OpenFOAM. Once the boundary conditions are set, the fluid dynamic calculations are performed using the OpenFOAM solver. Numerical results are validated by comparing them with the experimental data for a simple indoor air flow case. In this paper, an entirely new calculation process is introduced, and the flow simulation results for a sample office room are also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2610-2616
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• 2014

An ejector is a kind of pump which is using pressure energy of high pressure fluid. This study aims to investigate performance influencing according to change the ejector mixing section shape using CFD simulation by Finite Volume Method. Optimum conditions were suggested 3 kind of variable such as nozzle diameter, nozzle length, distance from nozzle tip to the diffuser inlet. The results, It was confirmed that the diameter of the nozzle was the greatest effect in performance of the ejector. The diameter of the nozzle get smaller, mixing ratio was increased. On the other hand, nozzle length, distance from nozzle tip to the diffuser inlet had little effect on performance. It was proposed specific Mixing section, Nozzel diameter 23.8mm using the Artificial Neural Network.

• Journal of the KSME
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• v.34 no.9
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• pp.705-710
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• 1994

열.유체유동 중 난류에 대한 유동현상은 매우 광범위한 영역에서 나타나기 때문에 그 응용성이 매우 크게 작용되어 상업용 설비, 항공기, 자동차, 연소기 및 각종 스포츠 등에 이르기까지 넓게 적용되고 있다. 본 계측법은 특히 기하학적 형상에 좌우되지 않는 범용데이터 처리와 결부시켜 이용하는 것으로 최근 컴퓨터의 보급이 활발히 정착됨에 따라 보다 정확한 방법으로 난류의 정량적인 자료와 정성적인 난류구조를 계측하기 위하여 컴퓨터와 온라인으로 연결한 열선한 열 선유속계의출력을 통계해석에 의해 분석하는 방법이 시도되고 있는 것이다. 끝으로 이 글에서 언급한 삼축 열선 프로브는 프로브의 제작에 대한 고도의 기술과 프로브의 겁사체적을 되도록 작게 해야 하는 과제를 안고 있으며, 이러한 문제들은 제작기술의 발달로 점차 해결되고 있으며 적용대상이 크기 때문에 앞으로 많이 이용 될 것으로 기대되는 바이다.