• Title/Summary/Keyword: Viscous Flow Field

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Numerical Analysis of Incompressible Viscous Flow with Free Surface Using Pattern Filling and Refined Flow Field Regeneration Techniques (형상충전기법과 세분화된 유동장 재생성기법을 이용한 자유표면을 가진 비압축성 점성유동의 수치적 모사)

  • Jeong, Jun-Ho;Yang, Dong-Ryeol
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.3
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    • pp.933-944
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    • 1996
  • In this paper, two new techniques, the pattern filling and the refined flow field regeneration, based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible viscous flow with free surfaces. The gorerning equation for flow analysis is Navier-Stokes equation including inertia and gravity effects. The penalty and Newton-Raphson methods are used effectively for finite element formulation. The flow front surface and the volume inflow rate are calculated using the pattern filling technique to select an adequate pattern among five filling patterns at each quadrilateral control volume. By the refined flow field regeneration technique, the new flow field which renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. Using the new thchniques to be developed, the dam-breaking problem has been analyzed to predict flow phenomenon of fluid and the predicted front positions versus time have been compared with the reported experimental result.

Development of Wave and Viscous Flow Analysis System for Computational Evaluation of Hull Forms

  • Kim, Wu-Joan;Kim, Do-Hyun;Van, Suak-Ho
    • Journal of Ship and Ocean Technology
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    • v.4 no.3
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    • pp.33-45
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    • 2000
  • A computational system for wave and viscous flow analysis (WAVIS) has been developed. The system includes a pre-processor, flow solvers and a post-processor. The pre-processor is composed of full form presentation, surface mesh and field grid generation. The flow solvers are for potential and viscous flow calculation. The post-processor has graphic utility for result analysis. All the programs are integrated in a GUI-launcher package. To validate the developed CFD programs of WAVIS, the calculated results for modern commercial hull forms are compared with measurements. It is found that the results from WAVIS are in good agreement with the experimental data, illustrating the accuracy of the numerical methods employed for WAVIS.

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UNSTEADY HARTMANN FLOW WITH HEAT TRANSFER IN THE PRESENCE OF UNIFORM SUCTION AND INJECTION

  • Attia Hazem A.
    • The Pure and Applied Mathematics
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    • v.13 no.1 s.31
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    • pp.1-10
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    • 2006
  • The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to a constant pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the magnetic field and the uniform suction and injection on both the velocity and temperature distributions is examined.

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Stability analysis of gas-liquid interface using viscous potential flow (점성포텐셜유동을 이용한 이상유동장의 표면안정성 해석)

  • Kim, Hyung-Jun;Kwon, Se-Jin
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.3033-3038
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    • 2007
  • In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.

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A STUDY OF INCOMPRESSIBLE VISCOUS FLOW ANALYSIS BY VORTEX-IN-CELL METHOD (보오텍스 인 셀 방법을 이용한 점성유동해석 연구)

  • Lee, J.H.;Kim, Y.C.;Lee, K.J.;Suh, J.C.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.78-85
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    • 2011
  • The Vortex-In-Cell(VIC) method combined with panel method is applied to the analysis of incompressible unsteady viscous flow. The dynamics of resulting flow is governed by the vorticity transport equation in Lagrangian form with vortex particle representation of the flow field. A regular grid which is independent to the shape of a body is used for numerical evaluation based on immersed boundary technique. With an introduction of this approach, the development and validation of the VIC method is presented with some computational results for incompressible viscous flow around two or three dimensional bodies such as wing section, sphere, finite wing and marine propeller.

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Numerical Analysis of Unsteady Viscous Flow Through a Weis-Fogh Type Ship Propulsion Mechanism Using the Advanced Vortex Method

  • Ro Ki-Deok;Kang Myeong-Hun;Kong Tae-Hee
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.7
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    • pp.769-778
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    • 2005
  • The velocity and pressure fields of a ship's Weis-Fogh type propulsion mechanism are studied in this paper using an advanced vortex method. The wing (NACA0010 airfoil) and channel are approximated by source and vortex panels. and free vortices are introduced away from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. The velocity is calculated on the basis of the generalized Biot-Savart law and the pressure field is calculated from an integral, based on the instantaneous velocity and vorticity distributions in the flow field. Two-dimensional unsteady viscous flow calculations of this propulsion mechanism are shown. and the calculated results agree qualitatively with the measured thrust and drag due to un-modeled large fluctuations in the measured data.

Viscous Flow Analysis around a Blade Section by a Hybrid Scheme Combining a Panel Method and a CFD Method (패널법과 전산유동해석법의 결합을 이용한 날개단면 주위 점성유동 해석)

  • Oh, Jin-An;Lee, Jin-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.50 no.5
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    • pp.355-363
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    • 2013
  • Panel methods are essential tools for analyzing a fluid-flow problem around complex three dimensional bodies, but they lack ability to solve viscous effects. On the other hand, CFD methods are considered as powerful tools for analyzing fluid-flow characteristics including viscosity. However, they also have short falls, requiring more computing time and showing different results depending on the selection of turbulence models and grid systems. In this paper a hybrid scheme combining a panel method and a CFD method is suggested. The scheme adopts a panel method for far-field solution where viscous effects are negligible and a CFD method for the solution of RANS equations in near-field where viscous effects are relatively strong. The intermediate region between the far-field and near-field is introduced where the calculated field point velocities by the panel method are given as boundary velocities for the CFD method. To verify the scheme, calculated results, by a panel method, a CFD method and the hybrid scheme, for a two dimensional foil section are compared. The suggested hybrid scheme gives reasonable results, while computation time and memory can be dramatically reduced. By using the hybrid scheme efforts can be concentrated for the local flow near the leading and trailing edges, by providing more dense grid system, where detailed flow characteristics are required.

Numerical study of Three-Dimensional Viscous Flow and Compression Wave Induced by the High Speed Train Entering into a Tunnel (터널에 진입하는 고속전철 주위의 3차원 점성유동과 압축파 특성에 관한 수치해석적 연구)

  • Shin C. H.;Park W. G.
    • Journal of computational fluids engineering
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    • v.5 no.3
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    • pp.23-31
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    • 2000
  • The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the viscous flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation owing to the viscous interaction around the train was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed.

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Numerical Analysis on the Flow Field and Heat Transfer Characteristics of Longitudinal Vortices in Turbulent Boundary Layer - On the Common Flow Up - (3차원 난류경계층 내에 존재하는 종방향 와동의 유동장 및 열전달 특성에 관한 수치해석(II) - Common Flow Up에 관하여 -)

  • Yang Jang-Sik
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.9
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    • pp.799-807
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    • 2005
  • The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

Calculation of 3-Dimensional Flow Through an Impeller of Centrifugal Compressor (원심압축기 회전차 내부의 3차원 유동해석)

  • ;;Kang, S. H.;Jeon, S. G.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.10
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    • pp.2617-2629
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    • 1995
  • The flow through a centrifugal compressor rotor was calculated using the quasi-3-dimensional and fully 3-dimensional Navier-Stokes solution methods. The calculated results, obtained during the development of the computer codes for both methods are discussed. In the inviscid quasi 3-dimensional analysis, stream function formulation was used for the blade to blade (B-B) plane calculations, and the streamline curvature method was used for the meridional (H-S) plane calculations. In the viscous 3-dimensional flow analysis, a control volume method based on a general rotating curvilinear coordinate system was used to solve the time-averaged Navier-Stokes equations, and a standard k-.epsilon. model was used to obtain eddy viscosity. The quasi-3-dimensional analysis reasonably predicts the pressure distributions and requires much less computation time in the region where viscous effects are not strong; however, it fails to predict velocity field and loss mechanism through the impeller passage. The viscous 3-dimensional flow analysis shows reasonable pressure distributions and typical jet-wake flow field through the impeller passage. Secondary flow and total pressure distributions on cross-sectional planes explain the loss mechanisms through the impeller.