• Title/Summary/Keyword: Finite Cylinder

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Wind pressures on different roof shapes of a finite height circular cylinder

  • Ozmen, Y.;Aksu, E.
    • Wind and Structures
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    • v.24 no.1
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    • pp.25-41
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    • 2017
  • The effects of finite cylinder free end shape on the mean and fluctuating wind pressures were investigated experimentally and numerically by using three different roof shapes: flat, conical and hemispherical. The pressure distributions on the roofs and the side walls of the finite cylinders partially immersed in a simulated atmospheric boundary layer have been obtained for three different roof shapes. Realizable $k-{\varepsilon}$ turbulence model was used for numerical simulations. Change in roof shapes has caused significant differences on the pressure distributions. When compared the pressure distributions on the different roofs, it is seen from the results that hemispherical roof has the most critical pressure field among the others. It is found a good agreement between numerical and experimental results.

A Study on the Behavior of Ambient Hydraulic Cycling Test for 70 MPa Type3 Hydrogen Composite Cylinder (70 MPa용 Type 3 수소 복합용기의 상온수압반복 거동에 관한 연구)

  • Cho, Sung-Min;Kim, Chang-Jong;Kim, Young-Gyu
    • Journal of the Korean Institute of Gas
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    • v.16 no.1
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    • pp.46-50
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    • 2012
  • The performance of the Type3 hydrogen composite cylinder whose pressure is 70 MPa using hydrostatic cycling test equipment was evaluted in this study. It also includes the finite element method analysis on the performance of the cylinder when the pressure is applied. As a result, cylinder body parts of the Type3 hydrogen composite cylinder, which draws attention with its safe status and the lightness, was ruptured first and the same result has been found out through the finite element method. The dome knuckle and the cylinder body were proved as the weakest parts since the cylinder body parts was expanded under the pressure.

Second-order wave radiation by multiple cylinders in time domain through the finite element method

  • Wang, C.Z.;Mitra, S.;Khoo, B.C.
    • Ocean Systems Engineering
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    • v.1 no.4
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    • pp.317-336
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    • 2011
  • A time domain finite element based method is employed to analyze wave radiation by multiple cylinders. The nonlinear free surface and body surface boundary conditions are satisfied based on the perturbation method up to the second order. The first- and second-order velocity potential problems at each time step are solved through a finite element method (FEM). The matrix equation of the FEM is solved through an iteration and the initial solution is obtained from the result at the previous time step. The three-dimensional (3D) mesh required is generated based on a two-dimensional (2D) hybrid mesh on a horizontal plane and its extension in the vertical direction. The hybrid mesh is generated by combining an unstructured grid away from cylinders and two structured grids near the cylinder and the artificial boundary, respectively. The fluid velocity on the free surface and the cylinder surface are calculated by using a differential method. Results for various configurations including two-cylinder and four-cylinder cases are provided to show the mutual influence due to cylinders on the first and second waves and forces.

Elastodynamic and wave propagation analysis in a FG graphene platelets-reinforced nanocomposite cylinder using a modified nonlinear micromechanical model

  • Hosseini, Seyed Mahmoud;Zhang, Chuanzeng
    • Steel and Composite Structures
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    • v.27 no.3
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    • pp.255-271
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    • 2018
  • This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

A study on the elastic-plastic analysis and fracture behavior of pressure vessel (내외압을 받는 압력용기의 탄소성 해석과 파괴거동에 대한 고찰)

  • 엄동석
    • Journal of Welding and Joining
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    • v.6 no.2
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    • pp.19-29
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    • 1988
  • This paper reports on the elatic-plastic analysis and fracture behavior of cylinder with outer surface crack which is under external or internal pressure. For the studuty of crack length effects in cylinder, ratios of crack lengths to finite thickness (a/t) are dertermined 0.3, 0.4, 0.5. For the study of curvature effects in cylinders, ratios of mean diameter to finite thicknees (Rm/t) are determined 10.0, 15.0, 20.0. Analysis is conduceted using the theory of fracture mechanics and two dimensional finite element solution assuming the axi-symmetrical plane strain conditon. Main results of this study are as follows. 1) It is known from this paper that elastic-plastic strain is initiated near crack tip and enlarged between crack tip and inner side of cylinder. 2) $K_{1}$ of cylinder under external or internal pressure is evaluated memebrane stress .root..pi.* crack length. The results of this study are inclined to Lomacky's results and Kobayshi's result. 3) Distribution of stress near crack tip is looked higher than of other zone, as crack length of equal model is longer, and as diameter of cylinder is longer. 4) When other conditions are equal, displacemenet near crack tip is looked duller, as length is longer.

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Study on the Thermal Stress Distribution Characteristivs of the Cylinder Block of a Light Gasoline Engine (경차용 가솔린 기관 실린더 블럭의 열응력 분포 특성에 대한 연구)

  • 김병탁
    • Journal of Advanced Marine Engineering and Technology
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    • v.22 no.6
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    • pp.800-808
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    • 1998
  • In this study the thermal stress distribution and deformantion characteristics resulting from the nonuniform temperature fields of the cylinder block of a light 3-cylinder 4-stroke gasoline engine were analyzed using the 3-dimensional finite element method. The temperature distributions req-uisite for the thermoelastic behavior alalysis were obtained from the steady-state heat conduction analysis performed on the basis of experimental data. in order to examine the effect of a ceramic material the cylinder liner was replaced by the silicon nitride($Si_{3}N_{4}$) and its thermal behaviors were compared with those of the original block.

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Heat Conduction of the Solidification Process in a Cylinder with Finite Thichness (유한두께를 가지는 원형관내의 응고과정의 열전도)

  • ;;Ro, Sung Tack
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.1 no.4
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    • pp.196-202
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    • 1977
  • The solidification process in a cylinder with finite thickness in studied by explicit finite difference method. The temperature distribution, the solidification front profile and the dischrged latent heat for the process are obtained. It is found that the solidification front profile is almost linear except in the vicinity of the initation of phase change. This result motivates us to use linear relations between the position of solidification and time for approximate calculations.

Thermal Behavior Analysis on the Cylinder Block of an Automotive Gasoline Engine (자동차용 가솔린 기관의 실린더 블록에 대한 열적 거동 해석)

  • 손병진;김창헌
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.5
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    • pp.211-221
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    • 1998
  • Thermal behavior on the cylinder block of a 4-cylinder, 4-stroke 2.0L SOHC gasoline engine was numerically and experimentally analyzed. The numerical calculation was performed using the finite element method. The cylinder block was modelled as a three dimensional finite element by considering its geometry. The physical domain was devided into hexahedron elements. 16 thermocouples were installed at points of 2mm inside from cylinder wall near top ring of piston in cylinder block, which points have suffered major thermal loads and suggested as proper measurement points for engine design by industrial engineers. Under full load and 9$0^{\circ}C$ coolant temperature condition, temperature behavior of cylinder block according to engine speed were analyzed. The results showed that temperature rose gradually to conform to a function of 2nd~4th order of engine speed at intake side, exhaust and siamese side, respectively. As engine load was changed from 100 to 50% by 25% step, temperature curve also conformed to 2nd~7th order function of engine speed. Temperature differences by load condition were similar among 100, 75% and 50%. Under full load and coolant temperature of 11$0^{\circ}C$, temperature behavior were also analyzed and the result also showed conformance to 2n d~7th order function of engine speed. Temperature curve was transferred in parallel upwards corresponding coolant temperature rise.

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Direct Numerical Simulation of the Flow Past an Oscillating Circular Cylinder (진동하는 원주주위 유동의 직접수치해석)

  • Kang S. J.;Tanahashi M.;Miyauchi T.;Lee Y. H.
    • Journal of computational fluids engineering
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    • v.6 no.4
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    • pp.26-34
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    • 2001
  • The flow past a circular cylinder forced to vibrate transversely is numerically simulated by solving the two-dimensional Navier-Stokes equations modified by the vibration velocity of a circular cylinder at a Reynolds number of 164. The higher-order finite difference scheme is employed for the spatial discretization along with the second order Adams-Bashforth and the first order backward-Euler time integration. The calculated cylinder vibration frequency is between 0.60 and 1.30 times of the natural vortex-shedding frequency. The calculated oscillation amplitude extends to 25% of the cylinder diameter and in the case of the lock-in region it is 60%. It is made clear that the cylinder oscillation has influence on the wake pattern, the time histories of the drag and lift forces, power spectral density and phase diagrams, etc. It is found that these results include both the periodic (lock-in) and the quasi-periodic (non-lock-in) state. The vortex shedding frequency equals the driving frequency in the lock-in region but is independent in the non-lock-in region. The mean drag and the maximum lift coefficient increase with the increase of the forcing amplitude in the lock-in state. The lock-in boundaries are also established from the present direct numerical simulation.

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Direct Numerical Simulation of the Flow Past an Oscillating Circular Cylinder (진동하는 원주주위 유동의 직접수치해석)

  • KANG Shin-Jeong;TANAHASHI Mamoru;MIYAUCHI Toshio;NAM Cheong-Do;LEE Young-Ho
    • 한국전산유체공학회:학술대회논문집
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    • 2001.05a
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    • pp.181-188
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    • 2001
  • The flow past a circular cylinder forced to vibrate transversely is numerically simulated by solving the two-dimensional Wavier-Stokes equations modified by the vibration velocity of a circular cylinder at a Reynolds number of 164. The higher-order finite difference scheme is employed for the spatial discretization along with the second order Adams-Bashforth and the first order backward-Euler time integration. The calculated cylinder vibration frequency is between 0.60 and 1.30 times of the natural vortex-shedding frequency. The calculated oscillation amplitude extends to $25\%$ of the cylinder diameter and in the case of the lock-in region it is $60\%$. It is made clear that the cylinder oscillation has influence on the wake pattern, the time histories of the drag and lift forces, power spectral density and phase diagrams, etc. It is found that these results include both the periodic (lock-in) and the quasi-periodic (non-lock-in) state. The vortex shedding frequency equals the driving frequency in the lock-in region but is independent in the non-lock-in region. The mean drag and the maximum lift coefficient increase with the increase of the forcing amplitude in the lock-in state. The lock-in boundaries are also established from the present direct numerical simulation.

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