• 한국가시화정보학회지
• /
• 제4권2호
• /
• pp.59-68
• /
• 2006

We have evaluated the performances of the following six interpolation schemes used for win-dow deformation in particle image velocimetry (PIV): the linear, quadratic, B-spline, cubic, sinc, Lagrange interpolations. Artificially generated images comprised of particles of diameter in a range pixel were investigated. Three particle diameters were selected for detailed evaluation: pixel with a constant particle concentration $0.02particle/pixel^2$. Two flow patterns were considered: uniform and shear flows. The mean and random errors, and the computation times of the interpolation schemes were determined and compared.

• 한국전산유체공학회지
• /
• 제12권4호
• /
• pp.28-37
• /
• 2007

In this study, a multi-block structured grid deformation code based on a hybrid of a transfinite interpolation algorithm and spring analogy was developed. The configuration was modeled by a Bezier surface. A combination of the spring analogy for block vertices and the transfinite interpolation for interior grid points helps to increase the robustness and makes it suitable for distributed computing. An elliptic smoothing operator was applied to the block faces with sub-faces in order to maintain the grid smoothness and skewness. The capability of this code was demonstrated on a range of simple and complex configurations including an airfoil and a wing-body configuration.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 춘계학술대회논문집
• /
• pp.283-289
• /
• 2009

In level set method, material properties are made to change smoothly across an interface of two materials with different properties by introducing an interpolation or smoothing scheme. So far, the weighted arithmetic mean (WAM) method has been exclusively adopted in level set method, without complete assessment for its validity. We showed here that the weighted harmonic mean (WHM) method for rate constants of various rate processes, including viscosity, thermal conductivity, electrical conductivity, and permittivity, gives much more accurate results than the WAM method. The selection of interpolation scheme is particularly important in multi-phase electrohydrodynamic problems in which driving force for fluid flow is electrical force exerted on the phase interface. Our analysis also showed that WHM method for both electrical conductivity and permittivity gives not only more accurate, but also more physically realistic distribution of electrical force at the interface. Our arguments are confirmed by numerical simulations of drop deformation under DC electric field.

• ETRI Journal
• /
• 제33권2호
• /
• pp.295-298
• /
• 2011

We propose a motion-compensated frame interpolation method in which an accurate backward/forward motion vector pair (MVP) is estimated based on a parabolic motion model. A reliability measure for an MVP is also proposed to select the most reliable MVP for each interpolated block. The possibility of deformation of bidirectional corresponding blocks is estimated from the selected MVP. Then, each interpolated block is produced by combining corresponding blocks with the weights based on the possibility of deformation. Experimental results show that the proposed method improves PSNR performance by up to 2.8 dB as compared to conventional methods and achieves higher visual quality without annoying blockiness artifacts.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2006년도 추계학술대회 논문집
• /
• pp.25-35
• /
• 2006

We have evaluated the performances of the following six interpolation schemes used for window deformation in particle image velocimetry (PIV): the linear, quadratic, B-spline, cubic, sinc, Lagrange interpolations. Artificially generated images comprised of particles of diameter in a range $1.1{\leq}d_p\leq10.0$ pixel were investigated. Three particle diameters were selected for detailed evaluation: $d_p$=2.2, 3.3, 4.4 pixel with a constant particle concentration 0.02 $particle/pixel^2$. Two flow patterns were considered: uniform and shear flows. The mean and random errors, and the computation times of the interpolation schemes were determined and compared.

• 한국산학기술학회논문지
• /
• 제12권11호
• /
• pp.5347-5356
• /
• 2011

본 연구에서는 Lagrangian/Hermite 보간함수를 혼합정식화한 유한요소법과 다양한 전단변형함수로 역대칭 앵글-플라이 샌드위치판 모델을 비교하였다. 제시된 전단변형함수는 판의 상하면에서 전단응력이 0이 되는 다항식, 삼각함수, 쌍곡삼각함수 및 지수함수로 구성되어 있다. 모든 전단변형함수는 해석해(Analytical solution)와 비교하였으며, 합리적인 정확도를 갖는 것으로 예측되었다. 특히, 지수형태의 전단변형함수가 복합면재를 갖는 샌드위치판 해석에 있어서 상대적으로 가장 우수한 결과를 보였다.

• 대한산업공학회지
• /
• 제20권2호
• /
• pp.77-90
• /
• 1994

Curve-net interpolation surface is one of the most popular method in engineering design. Therefore it is supported with many commercial CAD/CAM system. However, construction algorithm of curve-net interpolation surfaces is rarely opened to the public because of its copy-right. In this paper we establish a construction algorithm of curve-net interpolation surface so called sweeping surface which especially concentrates on trajectory of cross-section curve. We also show the method which can construct sweeping surfaces as NURB or Bezier mathematical models. Surfaces having the form of standard mathematical models are very useful for the application of joining, trimming, blending etc. The proposed surface interpolation scheme consists of four steps; (1) preparation of guide curves and section curves, (2) remeshing guide curves and section curves, (3) blending section curves after deformation, and (4) determination of control points for sweeping surface using gordon method. The proposed method guarantee $G^1$-continuety, and construct the surface salifying given section curves and trajectory of section curves.

• 한국항공우주학회지
• /
• 제36권11호
• /
• pp.1049-1055
• /
• 2008

최근 다분야 전산유체 역학에서는 설계 최적화, 공탄성, 강제 경계 운동 등에서 요구되어지는 이동경계문제를 다루게 된다. 이동경계의 변위가 클 경우 강건하고 효율적인 격자 변형 알고리즘의 개발이 필요하다. 본 연구에서는 유한 대형요소와 초월유한보간에 근거한 체적격자 변형 코드를 개발하였고, 정렬격자 다중 블록 Navier-Stokes 코드와 연계하였다. 개발된 코드의 검증을 위해 주기적으로 진동 운동을 하는 에어포일 문제에 대해 계산을 수행 하였고 양력, 항력, 모멘트 계수의 이력 계산 결과가 실험 결과와 잘 일치하였다.

• Structural Engineering and Mechanics
• /
• 제40권2호
• /
• pp.191-213
• /
• 2011

This paper presents an improved 8-node shell element for the analysis of plates and shells. The finite element, based on a refined first-order shear deformation theory, is further improved by the combined use of assumed natural strain method. We analyze the influence of the shell element with the different patterns of sampling points for interpolating different components of strains. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Further, a refined first-order shear deformation theory, which results in parabolic through-thickness distribution of the transverse shear strains from the formulation based on the third-order shear deformation theory, is proposed. This formulation eliminates the need for shear correction factors in the first-order theory. Numerical examples demonstrate that the present element perform better in comparison with other shell elements.

• 한국항공우주학회지
• /
• 제36권6호
• /
• pp.532-540
• /
• 2008

최근 구조변형을 고려한 항공기의 공력특성을 계산하는데 필요한 CFD와 CSD 기법이 연계된 FSI 시스템에 관한 관심이 증대하고 있다. 본 연구에서는 유체유발 구조 변형을 고려한 수렴된 구조형상에 대한 공력특성 예측을 위해 유체-구조 연계 시스템인 FSI(Fluid- Structure Interaction)를 구축하였다. 각 모듈의 연계, 특히 CSD와 CFD의 결합 및 변형된 형상에 대한 공력격자 재생성을 위해 VSI(Volume Spline Interpolation)와 격자 변형 코드를 개발하였으며, 공력과 구조의 해석 모듈로 상용 프로그램인 FLUENT와 NASTRAN을 사용하였다. 구축된 시스템을 DLR-F4 날개에 적용하여 정적 유체-구조 연구를 수행하였으며, 그 결과 마하수 0.75에서 변형된 형상에 대한 양력 및 항력 계수는 약 20.26%, 18.5% 감소하는 것으로 나타났다.