• Transactions on Control, Automation and Systems Engineering
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• 제3권4호
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• pp.268-271
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• 2001

In this paper, we propose a simplified pollution adaptive mesh generation algorithm using singular elements. The algorithm based on the element pollution error indicator concentrate on boundary nodes. The automatic mesh generation method is followed by either a node-relocation or a node-insertion method. The boundary node relocation phase is introduced to reduce pollution error estimates without increasing the boundary nodes. The node insertion phase greatly improves the error and the factor with the cost of increasing the node numbers. It is shown that the suggested r-h version algorithm combined with singular elements converges more quickly than the conventional one.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.610-615
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• 2003

This experiment has been carried out to find the structure of turbulent boundary layer with instantaneous velocity fields obtained in stream-wall-normal planes using a stereo-PIV (Particle Image Velocimetry) method. And it has been measured perpendicular plane and horizontal plane with hairpin vortex structure by Reynolds number change and made third dimension shape for section of horizontal plane through stereo-PIV. In the outer layer hairpin vortices occur in streamwise-aligned packets that propagate with small velocity dispersion. A streaky structure is composed of counter-rotating vortex. According as y+ increases, streaky structure's interval space decrease, and it shows that hairpin shape of prior research is vertified. The objective of the present research is to gain a better understanding of coherent structures in the outer of wall turbulence by experimentally examining coherent structures.

• Structural Engineering and Mechanics
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• 제21권3호
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• pp.315-332
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• 2005

The Element-free Galerkin Method has become a very popular tool for the simulation of mechanical problems with moving boundaries. The internally applied Moving Least Squares interpolation uses in general Gaussian or cubic weighting functions and has compact support. Due to the approximative character of this interpolation the obtained shape functions do not fulfill the interpolation conditions, which causes additional numerical effort for the application of the boundary conditions. In this paper a new weighting function is presented, which was designed for meshless shape functions to fulfill these essential conditions with very high accuracy without any additional effort. Furthermore this interpolation gives much more stable results for varying size of the influence radius and for strongly distorted nodal arrangements than existing weighting function types.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.246-252
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• 2000

This paper presents an explanatory study of combining the finite element and boundary element methods to achieve an efficient and accurate analysis of frame structure containing shear wall. This model analyzes the frame by finite element method and the shear wall by boundary element method. The purpose of this study is the specific case that boundary element is surrounded by finite element. If material properties of shear wall are relatively the very smaller than it of frame structure, the displacement shape of each node is calculated exactly. And if the solution of displacement is the larger, the displacement shape is approximated more accurately.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 봄 학술발표회 논문집
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• pp.3-10
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• 1997

Meshless particle method is a numerical technique which does not use the concept of element. This method can easily handle special engineering problems which cause difficulty in the use of finite element method, however it has a drawback that essential boundary condition is not satisfied. In this paper, several studies for satisfying essential boundary conditions and enhancing the accuracy of solutions are discussed. Particular emphasis is placed on a new numerical technique in which finite elements are used on the boundaries to satisfy the essential boundary conditions and meshless particle method is used in the interior domain. For coupling of the two methods interface elements are introduced into the zone between the subdomains using meshless particle method and finite element method. The shape functions and the approximated displacement functions of the interface element are derived with the ramp function based on the shape function of finite elements. The whole numerical procedures are formulated by Galerkin method. Several numerical examples for enhancing the accuracy of solution in the meshless particle method and a new coupling method are presented.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.117-120
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• 2002

An experimental research has been carried out for flow control of the shock wave/turbulent boundary-layer interaction utilizing aeroelastic mesoflaps. Various shapes and thicknesses of the mesoflap are tested to achieve different deflections of the flap, and ail the results are compared to the solid-wall reference case without flow-control mechanism. Quantitative variation of skin friction has been measured downstream of the interactions using the laser interferometer skin friction meter, and qualitative skin friction distribution has been obtained by observing the interference fringe pattern on the oil-film surface. A strong spanwise variation in the fringe patterns with a narrow region of separation near the centerline is noticed to form behind the shock structure, which phenomenon is presumed partially related to three-dimensional flow structures associated with both the sidewalls and the bottom test surface. The effect of the shape of the cavity is also observed and it is noticed that the shape of the cavity is not negligible.

• 대한기계학회논문집A
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• 제24권3호
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• pp.645-652
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• 2000

A method for shape design sensitivity analysis is proposed utilizing commercial software ANSYS for thermal conduction problems. While the sensitivity formula is derived analytically by introduing adjoint variable concept, sensitivity calculation in practice as well as the primal and adjoint solution of thermal conduction is performed using the ANSYS very easily. Since the formula always takes boundary integral form, sensitivity evaluation in ANSYS requires a little more addition of post-processing routine which involves evaluation of boundary variable from the obtained solution. Though the BEM has been used as a better tool for this purpose, the present study shows it can also be calculated using any kind of analysis code such as ANSYS since the formula is based on analytic nature. Therefore the present study provides a new and efficient way of optimization which was not possible before using commercial software. The usefulness of the method is illustrated via a weight minimization problem of thermal diffuser.

• 대한조선학회논문집
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• 제52권3호
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• pp.255-264
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• 2015

Wind load and flow field of a drillship with respect to various super structures were experimentally investigated in KARI 1m-wide wind tunnel with an atmospheric boundary layer simulation. Six-component external balance and Particle image velocimetry technique were used to measure wind load and velocity vectors in the flow-field around the model respectively. The experimental model was an imaginary shaped drillship with an approximated model which has 1/640 scale compared with recent typical drillships. The test Reynolds number based on the overall length was about 1.5×10⁶. It was found that dominant factors influencing on ship wind load are cabin shape and cabin height. Round cabin has smaller axial wind load and narrow boundary layer around the ship than rectangular one, but its yawing moment at certain angles becomes higher. Low cabin height also show positive effects on axial wind load too. Hull shape and forecastle shape show relatively small influences on wind loads except for slight changes around ±45° wind directions.

• Computers and Concrete
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• 제13권6호
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• pp.781-798
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• 2014

Estimating the workability of self-compacting concrete (SCC) is very important both in laboratories and on construction site. A method using visual information during the mixing process was proposed in this paper to estimate the workability of SCC. First, fourteen specimens of concrete were produced by a single-shaft mixer. A digital camera was used to record all the mixing processes. Second, employing the digital image processing, the visual information from mixing process images was extracted. The concrete pushed by the rotating blades forms two boundaries in the images. The shape of the upper boundary and the vertical distance between the upper and lower boundaries were used as two visual features. Thirdly, slump flow test and V-funnel test were carried out to estimate the workability of each SCC. Finally, the vertical distance between the upper and lower boundaries andthe shape of the upper boundary were used as indicators to estimate the workability of SCC. The vertical distance between the upper and lower boundaries was related to the slump flow, the shape of the upper boundary was related to the V-funnel flow time. Based on these relationships, the workability of SCC could be estimated using the mixing process images. This estimating method was verified by three more experiments. The experimental results indicate that the proposed method could be used to automatically estimate SCC workability.

• 소성∙가공
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• 제5권2호
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• pp.122-129
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• 1996

The main objective of the study is to offer some basic information in relation to optimal shape and dimensions of the rotating band through the development of three-dimensional finite element method for metal forming analysis of the rotating band whose primary function is to impart spin to the projectile. The three-dimensional metal forming analysis of the rotating band has perfor-med by using recurrent boundary conditions. Such design factors as the outside diameter the total length and the profile of the rotating band must be considered carefully in order to design an optimal rotating band. Above design factors can be determined from such available analysis results as the deformed shape and the deformation load. of the rotating band and the normal pressure of the rotating band on a projectile shell. The remeshings are needed to carry out plastic deformation analysis with severe deformation through which the complete process analysis gets possible. The results can be utilized effectively in determining the optimal shape and size of the rotating band.