• Title/Summary/Keyword: 스톡스 유동

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Steady Stokes flow analysis using Axial Green's Function Formulation (축그린함수법을 이용한 정상상태의 스톡스유동해석)

  • Kim, D.W.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.256-258
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    • 2011
  • Using the axial Green's function method for Steady Stokes flows, we introduce a new pressure correction formula to satisfy the incompressibility condition, in which the pressure is related to the integral of the second order derivatives of the velocity. Based on this formula, we propose the iterative method for solving the Stokes flows in complicated domains. Even if the domain is complex, this method maintains the second order of convergence for the velocity.

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Effects of Characteristic Condition Number on Convergence in Calculating Low Mach Number Flows, II : Navier-Stokes Equations (저속 유동 계산의 수렴성에 미치는 특성 조건수의 영향 II : 나비어스톡스 방정식)

  • Lee, Sang-Hyeon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.2
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    • pp.123-130
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    • 2008
  • The effects of characteristic condition number on the convergence of preconditioned Navier-Stokes equations were investigated. The two-dimensional preconditioned Navier-Stokes adopting Choi and Merkle's preconditioning and the temperature preconditioning are considered. Preconditioned Roe's FDS scheme was adopted for spatial discretization and preconditioned LU-SGS scheme was used for time integration. It is shown that the convergence characteristics of the Navier-Stokes equations are strongly affected by the characteristic condition number. Also it is shown that the optimal characteristic condition numbers for viscous flows are larger than that in inviscid flows.

Stokes Flow Through a Microchannel with Projections of Constant Spacing (일정 간격의 돌출부를 갖는 마이크로채널 내의 스톡스 유동 해석)

  • Son, JeongSu;Jeong, Jae-Tack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.4
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    • pp.335-341
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    • 2015
  • In this study, we analyzed a two-dimensional Stokes flow through a microchannel containing projections with constant spacing attached to each wall. The projections on the top and bottom walls were semi-circular in shape, with in-phase locations. By considering the periodicity and symmetry of the flow, the eigenfunction expansion and least squared error method were applied to determine the stream function and pressure distribution. For some typical radius and spacing values, the streamline patterns and pressure distributions in the flow field are shown, and the shear stress distributions on the boundary walls are plotted. In addition, the average pressure gradients in the microchannel are also calculated and shown with the radius and spacing of the projections. In particular, the results for the case of extremely small gaps between the projections on the top and bottom walls are in good agreement with the lubrication results.

Study of Stokes Flow Past a Vertical Plate in a Two-Dimensional Channel (2차원 채널 내의 수직 평판을 지나는 스톡스 유동에 대한 연구)

  • Yoon, Seok-Hyun;Jeong, Jae-Tack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.6
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    • pp.609-615
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    • 2011
  • A two-dimensional Stokes flow past a vertical plate in a channel is analyzed. The vertical plate is located at the center of the channel, and plane Poiseuille flow exists far upstream and downstream of the vertical plate. The Stokes approximation is used, and the flow is investigated analytically using the method of eigenfunction expansion and the point collocation method. From the analysis, the stream function and pressure distribution are obtained, and the pressure and shear stress distributions on the plate and channel wall are calculated. The additional pressure drop induced by the vertical plate and the force exerted on it are calculated as functions of the length of the vertical plate. For a typical length of the vertical plate, the streamline pattern and pressure distribution are shown. In addition, numerical analysis of laminar flow with a small Reynolds number is carried out to analyze the effect of a small Reynolds number on the flow pattern.

Study on Stokes Flow Past Circular Cylinder in Two-Dimensional Channel (2차원 채널 내의 원형실린더를 지나는 스톡스 유동에 대한 연구)

  • Yoon, Seok-Hyun;Jeong, Jae-Tack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.10
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    • pp.895-900
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    • 2013
  • A two-dimensional Stokes flow past a circular cylinder in a channel is analyzed. The circular cylinder is located at the center of the channel, and a plane Poiseuille flow exists upstream and downstream far from the circular cylinder. The Stokes approximation is used, and the flow is investigated analytically by using the eigenfunction expansion and the least square methods. From the analysis, the stream function and pressure distribution are obtained, and the pressure and shear stress distributions on the circular cylinder and channel wall are calculated. The additional pressure drop induced by the circular cylinder and the force exerted on it are calculated as functions of the length of the radius of the circular cylinder. For a typical length of the radius of the circular cylinder, the streamline pattern and pressure distribution are shown.

Numerical Analysis of Viscous Flow on the Periodic Oscillating Flat Plate using Unsteady CFD Code (비정상 CFD 코드를 이용한 주기성 하모닉 진동 평판 위의 점성유동 수치해석)

  • Lee, Eunseok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.1000-1002
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    • 2017
  • Here, the unsteady Navier-Stokes solver has been developed using implicit dual time stepping method. The implicit dual time stepping method introduced the pseudo time step for solving the new residual including the steady state residual and real time derivative. For the validation of code, Stokes 2nd problem, the laminar flow on the oscillating flat plate was selected and compare the calculating results with analytic solutions. The calculating velocity profile and skin friction has a good agreement with analytic solutions.

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Analysis of Laminar Flows around Submerged Spheres (물 밑에 잠긴 구 주위의 층류 유동장 해석)

  • Kwag, Seung-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.8
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    • pp.1094-1099
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    • 2010
  • Three dimensional laminar flows are numerically simulated around the submerged spheres. The finite volume based Navier-Stokes equations with unstructured grids are solved to make clear the hydrodynamic phenomena near and far away from the body. Reviews are made on with the vorticity, velocity, dynamic pressure, residuals, drags, etc. The Reynolds numbers under consideration are 425, 300, 250 and 100. In case of small spacing between spheres, the flow is more stable than that past a single sphere. According to the analysis, the flow past two spheres is found to be unstable as the spacing becomes larger. The rear sphere shows the deduction of stagnation pressure, which results in the decrease of the resistance. The predicted drag coefficients verify that the present numerical calculation is reasonable.

Numerical Simulation of Turbulent Flows in Inlet Duct of Heat Recovery Steam Generator (배열회수 안내덕트 내부의 난류유동 수치시뮬레이션)

  • Kwag, Seung-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.6
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    • pp.809-813
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    • 2011
  • Turbulent flows are numerically simulated in the three dimensional inlet duct for heat recovery steam generator. The present study is aimed to analyze the effect of a variation in turbulent flow pattern by the change of roof angle in the transition duct. The finite volume based Navier-Stokes equations with unstructured grids are solved to make clear the flow dynamic phenomena. Reviews are made on with the data of path lines, velocity vectors, dynamic pressure, residuals for numerical convergence and so on. The k-epsilon, k-omega, Reynolds stress and RNG k-epsilon are used for generation of turbulence. Two types of roof angle are applied with and without the swirl in the duct. Turbulent flow patterns could be investigated for the optimum duct design based on the computational results.

AXISYMMETRIC STOKES FLOW PAST A DISK IN A CIRCULAR TUBE (원관 내의 디스크를 지나는 축대칭 스톡스 유동)

  • Jeong, Jae-Tack
    • Journal of computational fluids engineering
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    • v.21 no.4
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    • pp.96-101
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    • 2016
  • A two-dimensional Stokes flow past a circular disk in a circular tube is analyzed. The circular disk is located coaxially with the circular tube and the Hagen-Poiseuille flow exists at upstream and downstream far from the circular disk. The Stokes approximation is used and the flow is investigated analytically by using the method of eigenfunction expansion and the method of least square. From the analysis, the stream function and the pressure of the flow field are obtained, and the streamlines and pressure distribution are shown. Also, the pressure and shear stress distributions on the circular disk and circular tube wall are calculated, and shown for some typical radii of the circular disk. The additional pressure drop induced by the disk and the drag force exerted on the disk are compared as functions of the radius of the circular disk, and it is shown that the shear force on the wall of the tube increases due to the disk.

STOKES FLOW THROUGH A MICROCHANNEL WITH PROTUBERANCES OF STAGGERED ARRANGEMENT (엇갈린 배열의 돌출물들이 존재하는 마이크로채널 내의 스톡스 유동)

  • Son, Jeong Su;Jeong, Jae-Tack
    • Journal of computational fluids engineering
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    • v.20 no.4
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    • pp.109-115
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    • 2015
  • In this study, the Stokes flow in the microchannel is analysed where the semicircular protuberances with constant spacing are attached on the upper and lower walls with staggered arrangement. For the low Reynolds number flow in microchannel, Stokes approximation is used and the periodicity and symmetry of the flow are considered to determine the stream function and pressure distribution in the flow field by using the method of least squared error. As results, the streamline patterns and pressure distributions in the flow field are shown for some specific values of the size and spacing of the protuberances, and shear stress distributions on the surface of semicircular protuberances are plotted. Especially, for an important physical property, the average pressure gradient along the microchannel is obtained and compared with that for the case of in-phase arrangement of the upper and lower protuberances. And, for the small clearance between the protuberances of upper and lower walls or between the protuberances and the opposite wall, the average pressure gradient is derived from the lubrication theory and compared with that of the present study.