• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 추계학술대회논문집
• /
• pp.19-26
• /
• 2009

The objective of this study is to investigate aerodynamic characteristics of a Horizontal-axis wind turbines(HAWT), using CFD method with a commercial code STAR-CCM+ version 3.06. To verify the reliability of the computations, the CFD results are compared with the experimental ones of the National Renewable Energy Laboratory(NREL) Phase Ⅵ HAWT. For the comparison and examination of aerodynamic characteristics, the existent shape with a predesigned twist angle was replaced by the one with one-dimensional linear twist angle. In this study, the pressure contour and stream line around the blade were analyzed as main focus. Through this study the more efficient shape of airfoil is suggested with consideration of manufacturing cost.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.1497_1498
• /
• 2009

This paper presents the simulation of micro-lens arrays based on dry and wet etching technique. Code V (Optical Research Associates Ltd) simulation was performed to extract optimal design parameters of a Micro-Lens Array(MLA). Thickness of UV adhesive, wavelength of laser source, curvature, and shape of lens surface were chosen for the design parameters. The simulation results showed that focal length of a MLA decreased with the increase of UV adhesive thickness. And the focal length depended on shape of lens surface and length of laser source.

• 대한기계학회논문집B
• /
• 제40권8호
• /
• pp.519-525
• /
• 2016

펌프 성능 관점에서 바라보면 회전날개의 충격손실을 최소화하는 것은 매우 중요하다. 본 연구는 회전날개의 충격손실에 직접적으로 영향을 미치는 흡입 케이싱 내에 설치되는 안내깃의 형상 및 설치 각 변화가 축류 펌프의 성능에 미치는 효과를 수치 해석 방법을 통해 살펴보았다. 그리고 주어진 운전조건에서 흡입 케이싱 내에 설치되는 안내깃의 최적형상 및 설치 각을 최적화 기법을 사용하여 최적화하였다.

• Structural Engineering and Mechanics
• /
• 제7권1호
• /
• pp.111-126
• /
• 1999

The work presented here focuses on the development of suitable discretised formulations, for large-displacement shape and non-shape design sensitivity analysis (DSA), which enable the straightforward incorporation of structural optimisation into established finite element analysis (FEA) codes. For the generalised displacement-based functional the design sensitivity vector has been expressed in terms of displacement sensitivity. The Total Lagrangian formulation is utilised for modelling of large deformation of truss structures. The variational formulation of the sensitivity analysis procedure is discretised by using "pseudo" - finite elements, Results are presented for the sensitivity analysis and optimisation of standard truss structures. For the purposes of this work, the analysis and optimisation procedures outlined below are incorporated into the FEA code ABAQUS.

• 센서학회지
• /
• 제20권4호
• /
• pp.234-237
• /
• 2011

This paper presents a study into pH Indicator-Embedded hydrogel micro-particles which are encoded various shapes according to the captured indicator. We incorporate various pH indicators into a photo-curable hydrogel, PEG-DA(Poly(ethylene glycol) diacrylate). Using the latest fluidic lithography techniques, we can easily fabricate variously patterned hydrogel particles based on in-situ photopolymerization of the PEG-DA in a micro-fluidic channel. The shape of the particle is related to the pH indicator inside the particle. We demonstrate that the micro pH sensors change their colors according to the pH levels. The micro pH sensors have various characteristics that are related to the curing time, particle size, etc. By changing these conditions, we can adjust the long term stability and reaction time of the hybrid micro pH sensors.

• Journal of Advanced Marine Engineering and Technology
• /
• 제41권4호
• /
• pp.316-322
• /
• 2017

본 논문의 주 목적은 수치해석 도구를 활용하여 저항성능 관점에서 우수한 선형을 개발하는 것이다. 최종 개발된 선형의 성능 평가를 위해 수조 모형시험을 수행하였다. 현존선은 도면을 바탕으로 실물과 도면의 타당성 검토를 위해 실태조사를 수행하였다. 실태조사 시에 실제 운항 상태인 주 운항 배수량 및 주 운항 선속을 확인하였다. 수치해석을 바탕으로 현존선의 저항성능을 검토하였다. 개발선은 선수어깨의 파형개선, 배수량 분포의 균형화, 단면형상의 수정 그리고 중앙 스케그의 크기와 형상 변경에 관한 스터디를 통해 도출되었다. 수치해석 결과 개발선은 조파저항 개선에 의해 저항성능 관점에서 주 운항 선속인 11노트에서 약 15% 개선된 양을 보여주었다(Table 4 참조). 개발된 선형의 성능 평가를 위해서 수조 모형시험을 수행하였으며 그 결과 11노트에서 약 17% 개선된 양을 보여주었다(Table 5 참조).

• Structural Engineering and Mechanics
• /
• 제31권2호
• /
• pp.137-152
• /
• 2009

Mechanic behavior of Y-shape thin-walled box girder bridge structure is complex, so one can not exactly hold the mechanical behavior of the Y-shape thin-walled box girder bridge structure through general calculation theory and analytical method. To hold the mechanical behavior better, based on elementary beam theory, by increasing the degree of freedom analytical method, taking account of restrained torsiondistortion angledistortion warp and shearing lag effect at the same time, authors obtain a thin-walled box beam analytical element of 10 degrees of freedom of every node, derive stiffness matrix of the element, and code a finite element procedure. In addition, authors combine the obtained procedure with spatial grillage analytical method, meanwhile, they build a new analytical method that is the spatial thin-walled box girder element grillage analysis method. In order to validate the precision of the obtained analysis method, authors analyze a type Y-shape thin-walled box girder bridge structure according to the elementary beam theory analytical method, the shell theory analytical method and the spatial thin-walled box girder element grillage analysis method respectively. At last, authors test a type Y-shape thin-walled box girder bridge structure. Comparisons of the results of theory analysis with the experimental text show that the spatial thin-walled box girder element grillage analysis method is simple and exact. The research results are helpful for the knowledge of the mechanics property of these Y-shape thin-walled box girder bridge structures.

• 대한기계학회논문집A
• /
• 제37권5호
• /
• pp.631-640
• /
• 2013

본 논문에서는 R6 코드와 RCC-MR A16 코드에서 원주방향 균열 배관에 대해 제시하는 1,2 차 복합 하중하에서 J-적분 계산법에 대한 정량적인 비교를 하였다. 균열의 형상, 균열의 깊이, 2 차 하중의 크기 변수에 대한 유한요소 해석을 수행 하였고 유한요소 해석 결과를 이용해 각 코드의 J-적분 평가법에 대한 정량적인 비교를 하였다. R6 코드는 $L_r=1$ 부근에서 보수적으로 평가 되었으며 RCC-MR A16 코드의 경우 기계하중이 작은 영역에서 보수적으로 평가되었다. 이와 같은 결과를 토대로 본 논문에서는 원주방향 균열이 있는 배관에 대하여 각 코드의 J-적분 계산을 보완할 수 있는 방법을 제시하였다. 그 결과로 보완된 J-적분 계산이 유한요소해석 결과와 잘 일치하는 것을 확인 하였다.

• Steel and Composite Structures
• /
• 제43권2호
• /
• pp.271-278
• /
• 2022

Buckling is one of the most critical phoneme in the design of steel structures. Lateral torsional buckling (LTB) is particularly significant for slender beams generally subjected to loading in plane. The web distortion effects on LTB are not addressed explicitly in standards for flexural design of steel I-section members. Hence, the present study is focused to predict the influence of the web distortion on the elastic (L_r) limiting lengths given in American Institute of Steel Construction (AISC) code for the lateral torsional buckling (LTB) behavior of steel beams due to no provision in the code for consideration of web distortion. For this aim, the W44x335 beam is adopted in the buckling analysis carried out by the ABAQUS finite element (FE) program since it is one of the most critical sections in terms of lateral torsional buckling (LTB). The strain results at mid-height of the web at mid-span of the beam are taken into account as the monitoring parameters. The web strain results are found to be relatively greater than the yield strain value when L/L_r is equal to 1.0. In other words, the ratio of L/L_r is estimated from the numerical analysis to be about 1.5 when the beam reaches its first yielding at mid-span of the beam at mid-height of the section. Due to the effect of web distortion, the elastic limiting length (L_r) from the numerical analysis is obtained to be considered as greater than the calculated length from the code formulation. It is suggested that the formulations of the limiting length proposed in the code can be corrected considering the influence of the web distortion. This correction can be a modification factor or a shape factor that reduces sectional slenderness for the LTB formulation in the code.

• Computers and Concrete
• /
• 제17권1호
• /
• pp.107-127
• /
• 2016

Concrete is a heterogeneous material containing many weaknesses such as micro-cracks, pores and grain boundaries. The crack growth mechanism and failure behavior of concrete structures depend on the plastic deformation created by these weaknesses. In this article the non-linear finite element method is used to analyze the effect of presence of micro pore near a crack tip on both of the characteristics of crack tip plastic zone (its shape and size) and crack growth properties (such as crack growth length and crack initiation angle) under pure shear loading. The FE Code Franc2D/L is used to carry out these objectives. The effects of the crack-pore configurations and the spacing between micro pore and pre-excising crack tip on the characteristics of crack tip plastic zone and crack growth properties is highlighted. Based on the obtained results, the relative distance between the crack tip and the micro pore affects in very significant way the shape and the size of the crack tip plastic zone. Furthermore, crack growth length and crack initiation angle are mostly influenced by size and shape of plastic zone ahead of crack tip. Also the effects of pore decrease on the crack tip by variation of pore situation from linear to perpendicular configuration. The critical position for a micro pore is in front of the crack tip.