• Title/Summary/Keyword: Viscous Flow Simulation

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Quantitative rheology of polymers in high resolution structuring (미세성형공정에서의 폴리머 레올로지의 정량화)

  • Kim, Byeong-Hee;Kim, Heon-Young;Ki, Ho;Kim, Kwang-Soon;Kang, Shin-Ill
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1036-1042
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    • 2003
  • The hot embossing process has been mentioned as one of major nanoreplication techniques. This is due to its simple process, low cost, high replication fidelity and relatively high throughput. As the initial step of quantitating the embossing process , simple parametric study about embossing time have been carried out using high-resolution masters which patterned by the DRIE process and laser machining. Under the various embossing time, the viscous flow of thin PMMA films into microcavities during compression force has been investigated. Also, a study about simulating the viscous flow during embossing process has planned and continuum scale FDM analysis was applied on this simulation. With currently available test data and condition, simple FDM analysis using FLOW3D was made attempt to match simulation and experiment.

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Numerical Simulation on the Onset of Radial Fingering in a Hele-Shaw Cell or a Porous Medium

  • Min Chan Kim
    • Korean Chemical Engineering Research
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    • v.62 no.1
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    • pp.112-117
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    • 2024
  • Numerical simulations on the onset and the growth of viscous fingering during the miscible displacement due to the radial source flow were conducted. With introduction of a new stability criterion, the critical log-viscosity ratio, Rc, was found as a function of the Peclet number, Pe. Similar to the previous linear stability analyses, Pe made the system unstable, i.e., accelerated the onset of instability. For a large Pe system, the present numerical simulation yielded much stable results than the previous theoretical predictions This discrepancy was commonly encountered in the comparison between the theoretical prediction and the experimental finding. Additionally, the difference between the rectilinear system and the present one was also discussed. The present system was found more insensitive to the Peclet number than the rectilinear one.

The visual Simulation of Fluid Flow with Free Surface in a Virtual Water Tank (가상수조에서 자유표면을 가진 유체흐름의 가시화시뮤레이션)

  • 김남형;김남국
    • Journal of Ocean Engineering and Technology
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    • v.14 no.3
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    • pp.35-40
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    • 2000
  • SMAC method is, one of the numerical simulation techniques, modified from the original MAC for the time-dependent variation of fluid flows. The Navier-Stokes equation for incompressible time-dependent viscous flow is applied and, also marker particles which move with the fluid are used. Two-dimensional numerical computations of fluid flow are carried out in a virtual water tank. This paper has shown very well the movements of marker particles using SMAC method.

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Simulation of viscous and inviscid rayleigh-taylor instability with surface tension by using MPS

  • Kim, Kyung Sung;Kim, Moo Hyun
    • Ocean Systems Engineering
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    • v.8 no.2
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    • pp.167-182
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    • 2018
  • RTI (Rayleigh-Taylor instability) is investigated by a multi-liquid MPS (Moving Particle Semi-implicit) method for both viscous and inviscid flows for various density differences, initial-disturbance amplitudes, viscosities, and surface tensions. The MPS simulation can be continued up to the late stage of high nonlinearity with complicated patterns and its initial developments agree well with the linear theoretical results. According to the relevant linear theory, the difference between inviscid and viscous fluids is the rising velocity at which upward-mushroom-like RTI flow with vortex formation is generated. However, with the developed MPS program, significant differences in both growing patters and developing speeds are observed. Also, more dispersion can be observed in the inviscid case. With larger Atwood (AT) number, stronger RTI flows are developed earlier, as expected, with higher potential-energy differences. With larger initial disturbances, quite different patterns of RTI-development are observed compared to the small-initial-disturbance case. If AT number is small, the surface tension tends to delay and suppress the RTI development when it is sufficiently large. Interestingly, at high AT number, the RTI-suppressions by increased surface tension become less effective.

NUMERICAL SIMULATION OF UNSTEADY VISCOUS FLOWS USING A GRID DEFORMATION TECHNIQUE ON HYBRID UNSTRUCTURED MESHES (비정렬 혼합 격자계에서 격자 변형 기법을 이용한 비정상 점성 유동 수치 모사)

  • Lee, H.D.;Jung, M.S.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.04a
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    • pp.252-268
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    • 2009
  • In the present study, a grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were simulated to demonstrate the robustness of the present grid deformation technique.

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Performance Analysis of the Viscous-driven Micropump with Tandem Rotating Cylinders (한 쌍의 실린더를 가지는 점성구동 마이크로 펌프의 성능 해석)

  • Choi, Hyung-Il;Cho, Sung-Chan;Maeng, Joo-Sung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.9
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    • pp.1256-1261
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    • 2003
  • Since the viscous effect increases as the size of device decreases, viscous-driven micropump is a promising mechanism in microscale applications. In the present study, a dual-rotor type pump which contains two counter-rotating cylinders for improving performance characteristics is proposed. First, for flows in the single-rotor type pump, the present unstructured grid simulation method is validated by comparing its results to the previous results. Next, the performance of the dual-rotor type pump is evaluated by the parametric studies and is compared to that of the previous single-rotor type pump. The flow characteristics are qualitatively similar to those of single-rotor type pump. However, the performance of the micropump with tandem rotors is still better than that of previous pumping type, e.g. much larger flow rate, smaller driving region, higher efficiency, and wider operation range.

A Numerical Simulation based on Cell-centered Scheme for Contractive and Dilative Motion on Axisymmetric Micro-hydro machine (셀중심법에 의한 축대칭 극소 로봇의 압축팽창운동에 대한 수치적인 연구)

  • 강효길;김문찬;전호환
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.2
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    • pp.90-97
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    • 2004
  • Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid. An axisymmetric code is developed with unstructured grid system based on cell-centered scheme. It is validated by comparing with the results of Stokes approximation for the problem of uniform flow past a sphere in low Reynolds number(R$_{n}$=1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. In order to investigate the grid dependency, two different grids are applied to the present computations. The present study provides key information for the development of an axisymmetric Micro-hydro-robot.t.

A Numerical Simulation for Contractive and Dilative Periodic Motion on Axisymmetric Body

  • Kim, Moon-Chan
    • Journal of Ship and Ocean Technology
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    • v.3 no.1
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    • pp.1-11
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    • 1999
  • Numerical simulation for the axisymmetric body with contractive and dilative periodic motion is carried out. The present analysis shows that a propulsive force can be obtained in highly viscous fluid by the contractive and dilative motion of axisymmetric body. An axisymmetric code is developed with unstructured grid system for the simulation of complicated motion and geometry. It is validated by comparing with the results of Stokes approximation with the problem of uniform flow past a sphere in low Reynolds number($R_n$ = 1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. The simulation is extended to the analysis of waving surface with projecting part for finding out the difference of hydrodynamics performance according to variation of waving surface configuration. The present study will be the basic research for the development of the propulsor of an axisymmetric micro-hydro-machine.

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Numerical Analysis of Unsteady Viscous Flow through Ship's Propulsion Mechanism of Weis-Fogh Type by Advanced Vortex Method (최신 와법에 의한 Weis-Fogh형 선박추진기구의 비정상 점성 흐름의 수치해석)

  • Ro, Ki-Deok
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1407-1412
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    • 2004
  • The velocity and pressure fields of a ship's propulsion mechanism of Weis-Fogh type are studied by advanced vortex method. The wing of NACA0010 type and the channel are approximated by a finite of source and vortex panels, and the free vortices are introduced from the surface of their bodies. The viscous diffusion of fluid is represented by the core-spreading method. The velocity field is calculated on the basis of Biot-Savart law and the pressure field is calculated from the integration equation formulated by Uhlman. The flow fields of this propulsion mechanism are unsteady and complex, but the flow fields are clarified by numerical simulation.

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ANALYSIS OF TURBULENT BOUNDARY LAYER OF NATURAL CONVECTION CAUSED BY FIRE ALONG VERTICAL WALL (수직벽 화재 자연대류에 의한 난류 경계층 열유동 특성 해석)

  • Jang, Yong-Jun;Kim, Jin-Ho;Ryu, Ji-Min
    • Journal of computational fluids engineering
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    • v.21 no.4
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    • pp.1-10
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    • 2016
  • The analysis of characteristics of turbulent flow and thermal boundary layer for natural convection caused by fire along vertical wall is performed. The 4m-high vertical copper plate is heated and kept at a uniform surface temperature of $60^{\circ}C$ and the surrounding fluid (air) is kept at $16.5^{\circ}C$. The flow and temperature is solved by large eddy simulation(LES) of FDS code(Ver.6), in which the viscous-sublayer flow is calculated by Werner-Wengle wall function. The whole analyzed domain is assumed as turbulent region to apply wall function even through the laminar flow is transient to the turbulent flow between $10^9$<$Gr_z$<$10^{10}$ in experiments. The various grids from $7{\times}7{\times}128$ to $18{\times}18{\times}128$ are applied to investigate the sensitivity of wall function to $x^+$ value in LES simulation. The mean velocity and temperature profiles in the turbulent boundary layer are compared with experimental data by Tsuji & Nagano and the results from other LES simulation in which the viscous-sublayer flow is directly solved with many grids. The relationship between heat transfer rate($Nu_z$) and $Gr_zPr$ is investigated and calculated heat transfer rates are compared with theoretical equation and experimental data.