• 한국정밀공학회지
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• 제14권2호
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• pp.102-112
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• 1997

This paper describes the method that can construct kinematically admissible velocity fields for forging of gear-like components which have tooth shape around the cylinder. The kinematically admissible velo- city fields for the various gear-like components, involute spur gear, trapezoidal spline, square spline, ser- ration and trochoidal gear, were constructed by pilling up the velocity components according to the shape of tooth and billet. The billets, of hollow and solid, were Al 2218 and 2024. To verify the method, the analyses and experiments were carried out and compared with each other. For analyses, the half pitches of com- ponents were divided into several deformation regions based on their tooth profile. A neutral surface was used to represent the inner flow of material during forging. Its location varied with the energy optimazation and its contour varied with the number of teeth. In experiment, the contour of material filling up the tooth zone is hyperbolic curve caused by the frictional drag on the interface of die-wall/workpiece but, in the analysis, it is an arc which retains the same contour during all forging operation.

• 대한기계학회논문집B
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• 제32권1호
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• pp.62-69
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• 2008

A post-processing program based on the OOP(Object-Oriented Programming) concept has been developed for flow visualization of the flow analysis code(PowerCFD) using unstructured cell-centered method. User-friendly GUI(GTaphic User Interface) has been built on the base of MFC(Microsoft Foundation Class). The program is organized as modules by classes including those based on VTK(Visualization ToolKit)-library, and these classes are made to function through inheritance and cooperation which is an important and valuable OOP concept. The major functions of this post-processor program are introduced and demonstrated, which include mesh plot, contour plot, vector plot, surface plots, cut plot, clip plot, xy-plot and streamline plot as well as view manipulation (translation, rotation, scaling etc).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.13-16
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• 1999

An active contour model, Snake, was developed as a useful segmenting and tracking tool lot rigid or non-rigid (i.e. deformable) objects by Kass in 1987 In this research, Snake is newly designed to cover this large moving case. Image flow energy is proposed to give Snake the motion information of the target object. By this image flow energy Snake's nodes can move uniformly along the direction of the target motion in spite of the existences of local minima. Furthermore, when the motion is too large to apply image flow energy to tracking, a jump mode is proposed for solving the problem. The vector used to make Snake's nodes jump to the new location can be obtained by processing the image flow. The effectiveness of the proposed Snake is confirmed by some simulations.

• 한국전산유체공학회지
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• 제14권3호
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• pp.9-15
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• 2009

Numerical investigation has been carried out for laminar flow past an inclined square cylinder in cross freestream. In particular, inclination of a square cylinder with respect to the main flow direction can cause sudden shift of the separation points to other edges, resulting in drastic change of flow-induced forces on the cylinder such as Strouhal number (St) of vortex shedding, drag and lift forces on the cylinder, depending upon the inclination angle. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number on an Re-Angle plane. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards.

• 한국가시화정보학회지
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• 제13권1호
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• pp.30-34
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• 2015

This study concerns flow and heat transfer characteristics of FC-72 condensing flow in a micro-channel. A computational model of condensing flow with a hydraulic diameter of 1 mm is constructed using the FLUENT computational fluid dynamics code. The computed void fraction contour plots are presented for different mass velocities. The smooth-annular, wavy-annular, transition and slug flows are observed with the model, which are quite similar to those observed in a micro-channel experiment. The computed two-phase condensing heat transfer coefficient is compared with previous empirical correlation for two-phase condensation heat transfer in micro-channels.

• 한국기계가공학회지
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• 제12권3호
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• pp.21-27
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• 2013

This study is investigated on flow analysis according to grill configuration of radiator. The stream of flow which pass through radiator grill in car body and the contour of pressure distribution are estimated by the basis. As the magnitude of resistance force which flow affects the car body is investigated so that the power reduction can be reduced. As the pressure inside radiator grill is assessed, more efficiency can be investigated in order that the flow rate inside car body can be increased. Model 2 has the most air resistance and model 1 has the least among model 1, 2 and 3. Model 1 has the most air flow rate at inside. There are model 3 and 2 simulated according to flow rate. As the curved surface at radiator grill configuration increases in number, air flow rate becomes distributed uniformly. By considering the effect on air resistance and air flow rate at radiator grill, model 3 becomes the most effective configuration.

• 수산해양기술연구
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• 제38권1호
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• pp.43-57
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• 2002

본 연구는 고성능 전개판을 개발하기 위하여 전개판 주변의 유동장을 계측할 수 있는 해석 방법을 제시하고자 하였다. 실험 방법으로는 CFD를 이용한 유동장의 수치 해석과 유동장의 정량적, 정성적 계측이 가능한 PIV 실험방법을 사용하였다. 본 실험에서는 전개판 주변의 가시화된 영상을 PIV 기법을 이용한 화상처리로 유동특성을 해석하였으며, 이 결과를 CFD에 의한 해석 결과와 유동 패턴을 비교하였다. 또한, 회류 수조에서의 양력 계수 및 항력계수의 계측 결과를 상호 비교 하였다. 그 결과, 수치 해석된 결과와 PIV의 실험 결과는 정성적으로 매우 잘 일치하였으며, 물리적으로 타당성을 확인할 수 있었다. 그 결과는 다음과 같다. (1) 전개판의 유동장 분석을 위하여 레이저 광원을 이용한 가시화 실험을 실시하고, PIV 기법으로 화상분석을 실시하였으며, 유동입자의 흐름으로도 충분한 정성적인 유체운동의 경향을 파악할 수 있었다 (2) PIV해석결과가 정량적인 결과이므로 이를 다양한 후처리 방법을 통해 속도벡터장, 순간 유동장, 평균 와도로 나타내어 유동장의 변화를 확인할 수 있었다. (3) 최대전개력계수가 나타난 영각 24$^{\circ}$에서 비교한 CFD와 PIV 해석 결과, 유동 패턴은 유사하였고, 두 경우 모두 전개판 후연에서 약간의 경계층 박리가 발생하였으나 양호한 흐름을 보였다. (4) PIV에 의한 속도 벡터도, 순간 유선도, 평균 와도로 후처리한 결과, 영각 24$^{\circ}$에서부터 경계층 박리 현상이 일어나기 시작하여, 영각 28$^{\circ}$이상이 되면 심하게 전연으로 발생지점이 이동하게 되고, 그 폭도 확대됨을 확인할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.3-5
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• 2005

Vessel boundary detection and modeling is a difficult but a necessary task in analyzing the mechanics of inflammation and the structure of the microvasculature. In this paper we present a method of analyzing the structure by means of an active contour model(using GVF Snake) for vessel boundary detection and 3D reconstruction. For this purpose we used a virtual vessel model and produced a phantom model. From these phantom images we obtained the contours of the vessel by GVF Snake and then reconstructed a 3D structure by using the coordinates of snakes.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.376-379
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• 2010

Bubble rising phenomenon is widely founded in many industrial applications such as a stream generator in power plant. Many experimental and numerical researches have been already performed to predict dynamic behavior of the bubble rising process. Recently numerical approaches are getting popular since it can offer much detailed information which is almost impossible to obtain from the experiments. Rising bubble could penetrate through the top free surface which makes the problem much more complicate in addition to the phase changing effect even with latest numerical techniques. In this paper, the top free surface effect on rising bubble has been investigated. The gas-liquid interface was explicitly tracked using high-order Level Contour Reconstruction Method(LCRM) which is a hybridization of Front-Tracking and Level-Set method. Break-up behavior of rising bubble at free surface showed different characteristics with initial diameter of bubble.

• 대한조선학회지
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• 제15권4호
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• pp.20-23
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• 1978

This paper describes newly developed part generation program on the basis of ACUTE. New program named as ASEP(Automatic Separation Program) has function to separate a contour defined by ACUTE into several parts and store them in the part file. The separation flow is as follows, (1) Basic Contour Generation using ACUTE (2) Separation Line Definition (3) Separation into several parts (4) Storing parts in the part file with their individual name The merit of ASEP is to reduce the number of input cards and to simplify input statements.