• 제목/요약/키워드: Square cylinder

검색결과 206건 처리시간 0.022초

퇴화 쉘 요소를 사용한 적층복합재의 증분형 비선형 좌굴 현상 및 적층 레이업 효과 (The Effects of Composite Laminate Layups on Nonlinear Buckling Behavior Using a Degenerated Shell Element)

  • 조희근
    • 한국기계가공학회지
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    • 제15권1호
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    • pp.50-60
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    • 2016
  • Laminate composites have a number of excellent characteristics in aspects of strength, stiffness, bending, and buckling. Buckling and postbuckling analysis of laminate composites with layups of [90/0]2s, $[{\pm}45/90/0]s$, $[{\pm}45]2s$ has been carried using the Total Lagrangian nonlinear Newton-Raphson method. The formulation of a geometrically nonlinear composite shell element based on a nonlinear large deformation method is presented. The used element is an eight-node degenerated shell element with six degrees of freedom. Square, circular cylinder, and arch panel laminate geometries were analyzed to verify the effects of the layups on the buckling and postbuckling behavior. The results showed that the effects of laminate layups on bucking and postbuckling behavior and the present formulation showed very good agreement with existing references.

2차 정확도를 가지는 비정상 비압축성 유동장 해석을 위한 비정렬 유한 체적법의 개발 (An unstructured finite volume method for unsteady incompressible flows with full second order accuracy)

  • 이경세;백제현
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2004년도 춘계 학술대회논문집
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    • pp.71-76
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    • 2004
  • An extension of our recently developed locally linear reconstruction scheme to 2 dimensional incompressible flow solver is presented. The solver is based on a semi-implicit fractional step method in which the convective term is discretized by Adams-Bashforth method and the diffusion term by Crank-Nicolson method. Several numerical examples are tested to demonstrate the mesh type independent accuracy of the solver, which include decaying vortex flow, square cavity flow, and flow around a circular cylinder. The above examples are solved on quadrilateral or hybrid meshes. For all numerical examples, we obtained reasonable results.

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3차원 경사크랙을 가진 중공축의 응력확대계수산정 (Computation of stress Intensity Factors of Hollow Cylinder with Three Dimension Inclination Cracks)

  • 이종선
    • 한국생산제조학회지
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    • 제8권1호
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    • pp.21-27
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    • 1999
  • In this study, stress intensity factors KI, KII, KIII are existing at the same time to a hollow cylindrical bar of three dimension inclination crack. In order to investigate by experimentally the effect of the inclination angle $\psi$ of crack, artificial inclination cracks in the circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy-resin. Experimentally, stress analysis methods of stress intensity factors were proposed. But, suitable method are the caustic method and the photoelastic stress freezing method. The mixed mode of KI, and KII, were determined by the photoelastic method of the classical approach method and the FORTRAN language program of the used smallest square method.

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A POINT COLLOCATION SCHEME FOR THE STATIONARY INCOMPRESSIBLE NAVIER-STOKES EQUATIONS

  • Kim, Yongsik
    • 대한수학회보
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    • 제50권5호
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    • pp.1737-1751
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    • 2013
  • An efficient and stable point collocation scheme based on a meshfree method is studied for the stationary incompressible Navier-Stokes equations. We describe the diffuse derivatives associated with the moving least square method. Using these diffuse derivatives, we propose a point collocation method to fit in solving the Navier-Stokes equations which improves the stability of the direct point collocation scheme. The convergence of the numerical solution is investigated from numerical examples. The driven cavity ow and the backward facing step ow are implemented for the reliability of the scheme. Also, the viscous ow on complicated geometry is successfully calculated such as the ow past a circular cylinder in duct.

콘크리트의 압축강도에 공시체의 크기와 형상이 미치는 영향 (Effect of Specimen Sizes and Shapes on Compressive Strength of Concrete)

  • 최중철;양은익;이성태;김명유;이광교
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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    • pp.285-288
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    • 2003
  • The compressive strength of concrete is used as the most fundamental and important material property when reinforced concrete structures are designed. It has been problem to use this value, however, because the control specimen sizes and shapes are different from every country. In this study, the effect of specimen shapes and sizes on compressive strength of concrete members was experimentally investigated based on fracture mechanics. Experiments for the mode I failure was earned out by using cylinder, cube, and prism specimens. The test results are curve fitted using least square method(LSM) to obtain the new parameters for the modified size effect law(MSEL). The analysis results show that the effect of specimen sizes and shapes on ultimate strength is apparent. The results also show stronger size effect in member when the casting direction is perpendicular to loading direction

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2-방정식 난류모델을 이용한 정사각주 주위의 비정상 난류유동의 예측 (Towards Prediction of Unsteady Turbulent Flow over a Square Cylinder using Two-Equation Turbulence Models)

  • 이상산
    • 한국전산유체공학회지
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    • 제1권1호
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    • pp.47-54
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    • 1996
  • 비유선형 물체 주위의 유동은 정체유동, 경계층 박리 및 재부착, 주기적 와열의 생성등의 복잡한 유동현상이 공존한다. 이와 같은 유동의 2-방정식 난류모델을 이용한 정확한 예측은 일반적으로 불가능 하다고 인식되어 왔으나, 본 연구에서는 기존의 비교적 단순한 난류모델을 활용한 정사각주 주위의 비정상 난류유동의 예측 가능성을 체계적으로 규명하였다. 적절한 난류모델의 선정과 더불어 시간 정확도, 공간 정확도 및 대류항 처리법 등이 해석의 결과에 미치는 영향을 살펴 보았다. 기존의 표준 κ-ε모델은 정체점 주위에서 난류생성항의 과도한 예측으로 말미암아 재부착 및 와열생성의 정확한 예측이 불가능 하였으나, RNG κ-ε 모델을 사용한 경우 이와 같은 현상을 제거 할 수 있었다. 그러나 이 경우에도 예측의 정확도가 시간 증분, 격자의 크기 및 대류항 처리법 등에 영향을 받았으며, 특별히 대류항 처리법에 따라 상당히 민감하게 변하는 것을 알 수 있었다.

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ALE모델을 갖는 차분격자볼츠만법에 의한 이동물체 주위의 유동장 및 유동소음의 직접계산 (Direct Simulation of Flows and Flow Noise around Moving Body by FDLBM with ALE Model)

  • 강호근;;김명호;김유택;이영호
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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    • pp.248-249
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    • 2005
  • In this paper, flowfield and acoustic-field around moving bodies are simulated by the Arbitrary Lagrangian Eulerian (ALE) formulation in FDLBM. The effect of the ALE is checked by comparing flow about a square cylinder in ALE formulation and that in the fixed coordinates, and the results show good agreement. Matching procedure between the moving grid and fixed grid is also considered. The applied method in which the both grids are connected through buffer zone is shown to be superior to moving overlapped grid. Dipole-like emissions of sound wave from harmonically vibrating bodies in 2- and 3-dimensional cases are simulated.

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광학간섭계를 이용한 부착 혹은 박리된 열상승류를 갖는 등온수평정방형 실린더 주위의 자연대류에 관한 연구 (Interferometric Study on Natural Convection around an Isothermal Square Cylinder Having an Attached or Separated Plume)

  • 조철형;장근식
    • 대한기계학회논문집
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    • 제8권5호
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    • pp.498-504
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    • 1984
  • 가열된 곡면에 의한 자연대류에서는 유동의 박리현상이 존재하지 않음이 알려져 있다. 이에 반해 날카로운 모서리를 갖는 가열된 정방형 수평실린더에 의한 자연대류에서는 그라소프 수가 4.66*$10^{4}$ 전후로 부착 혹은 박리현상이 윗쪽 양 모서리 부근에서 일어남을 광학간섭 계(Mach Zehnder Inter-ferometer)를 이용하여 온도장을 가시화하고 이를 이용하여 좌우 대칭 선상에서의 속도분포를 간단한 대수적인 방법으로 구하여 수평정방형 윗쪽 수평면 위에 유동의 박리현상을 시사하는 "쌍동이 소용돌이"의 존재를 입증하였고, 이에 의해 온도역전현상과 평균 열전달량의 급격한 증가를 설명 할 수 있다.설명 할 수 있다.

Wave propagation in functionally graded composite cylinders reinforced by aggregated carbon nanotube

  • Moradi-Dastjerdi, Rasool
    • Structural Engineering and Mechanics
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    • 제57권3호
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    • pp.441-456
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    • 2016
  • This work reports wave propagation in the nanocomposite cylinders that reinforced by straight single-walled carbon nanotubes based on a mesh-free method. Moving least square shape functions have been used for approximation of displacement field in weak form of motion equation. The straight carbon nanotubes (CNTs) are assumed to be oriented in specific or random directions or locally aggregated into some clusters. In this simulation, an axisymmetric model is used and also the volume fractions of the CNTs and clusters are assumed to be functionally graded along the thickness. So, material properties of the carbon nanotube reinforced composite cylinders are variable and estimated based on the Eshelby-Mori-Tanaka approach. The effects of orientation, aggregation and volume fractions of the functionally graded clusters and CNTs on dynamic behavior of nanocomposite cylinders are studied. This study results show that orientation and aggregation of CNTs have significant effects on the effective stiffness and dynamic behaviors.

차분 래티스볼츠만법에 Subgrid 난류모델의 적용 (Application of Subgrid Turbulence Model to the Finite Difference Lattice Boltzmann Method)

  • 강호근;안수환;김정환
    • Journal of Advanced Marine Engineering and Technology
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    • 제30권5호
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    • pp.580-588
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    • 2006
  • Two-dimensional turbulent flows past a square cylinder and cavity noise are simulated by the finite difference lattice Boltzmann method with subgrid turbulence model. The method, based on the standard Smagorinsky subgrid model and a single-time relaxation lattice Boltzmann method, incorporates the advantages of FDLBM for handling arbitrary boundaries. The results are compared with those by the experiments carried out by Noda & Nakayama and Lyn et al. Numerical results agree with the experimental ones. Besides, 2D computation of the cavity noise generated by flow over a cavity at a Mach number of 0.1 and a Reynolds number based on cavity depth of 5000 is calculated. The computation result is well presented a understanding of the physical phenomenon of tonal noise occurred primarily by well-jet shear layer and vortex shedding and an aeroacoustic feedback loop.