• Title, Summary, Keyword: incompressible fluids

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Numerical Simulation of Free Surface Flows Using the Roe's Flux-difference Splitting Scheme (Roe의 Flux-difference Splitting 기법을 이용한 자유표면 유동 모사)

  • Shin, Sang-Mook;Kim, In-Chul;Kim, Yong-Jig
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.1
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    • pp.11-19
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    • 2010
  • A code is developed to simulate incompressible free surface flows using the Roe's flux-difference splitting scheme. An interface of two fluids is considered as a moving contact discontinuity. The continuities of pressure and normal velocity across the interface are enforced by the conservation law in the integral sense. The fluxes are computed using the Roe's flux-difference splitting scheme for two incompressible fluids. The interface can be identified based on the computed density distribution. However, no additional treatment is required along the interface during the whole computations. Complicated time evolution of the interface including topological change can be captured without any difficulties. The developed code is applied to simulate the Rayleigh-Taylor instability of two incompressible fluids in the density ratio of 7.2:1 and the broken dam problem of water-air. The present results are compared with other available results and good agreements are achieved for the both cases.

PARALLEL ALGORITHMS FOR INTEGRATION OF NAVIER-STOKES EQUATIONS BASED ON THE ITERATIVE SPACE-MARCHING METHOD

  • Skurin Leonid I.
    • Journal of computational fluids engineering
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    • v.10 no.1
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    • pp.67-72
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    • 2005
  • This research is based on the iterative space-marching method for incompressible and compressible Navier-Stokes equations[1-4]. A principle of parallel computational schemes construction for steady and unsteady problems is suggested. It is analytically proven that convergence of these schemes is unconditional for incompressible case. When the parallel scheme is used the total volume of computations is the sum of a large number of independent and equal parts. Estimation of the speed-up K shows that K > 1000 in ideal case. First results of using the parallel schemes are presented.

Incompressible/Compressible Flow Analysis over High-Lift Airfoils Using Two-Equation Turbulence Models (2-방정식 난류모델을 이용한 고양력 익형 주위의 비압축성/압축성 유동장 해석)

  • Kim C. S.;Kim C. A.;Rho O. H.
    • Journal of computational fluids engineering
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    • v.4 no.1
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    • pp.53-61
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    • 1999
  • Two-dimensional, unsteady, incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. The compressible code involves a conventional upwind-differenced scheme for the convective terms and LU-SGS scheme for temporal integration. The incompressible code with pseudo-compressibility method also adopts the same schemes as the compressible code. Three two-equation turbulence models are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by predicting the flow around the RAE 2822 transonic airfoil and the NACA 4412 airfoil, respectively. In addition, both the incompressible and compressible code are used to compute the flow over the NLR 7301 airfoil with flap to study the compressible effect near the high-loaded leading edge. The grid systems are efficiently generated using Chimera overlapping grid scheme. Overall, the κ-ω SST model shows closer agreement with experiment results, especially in the prediction of adverse pressure gradient region on the suction surfaces of high-lift airfoils.

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DEVELOPMENT OF AN UNSTRUCTURED HYBRID MESH FLOW SOLVER FOR 3-D STEADY/UNSTEADY INCOMPRESSIBLE FLOW SIMULATIONS (삼차원 정상/비정상 비압축성 유동해석을 위한 비정렬 혼합격자계 기반의 유동해석 코드 개발)

  • Jung, Mun-Seung;Kwon, Oh-Joon
    • Journal of computational fluids engineering
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    • v.13 no.2
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    • pp.27-41
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    • 2008
  • An unstructured hybrid mesh flow solver has been developed for the simulation of three-dimensional steady and unsteady incompressible flow fields. The incompressible Navier-Stokes equations with an artificial compressibility method were discretized by using a node-based finite-volume method. For the unsteady time-accurate computation, a dual-time stepping method was adopted to satisfy a divergence-free flow field at each physical time step. An implicit time integration method with local time stepping was implemented to accelerate the convergence in the pseudo-time sub-iteration procedure. The one-equation Spalart-Allmaras turbulence model has been adopted to solve high-Reynolds number flow fields. The flow solver was parallelized to minimize the CPU time and to overcome the computational overhead. This method has been applied to calculate steady and unsteady flow fields around submarine configurations and a 3-D infinite cylinder. Validations were made by comparing the predicted results with those of experiments or other numerical results. It was demonstrated that the present method is efficient and robust for the prediction of steady and unsteady incompressible flow fields.

EXISTENCE RESULT FOR HEAT-CONDUCTING VISCOUS INCOMPRESSIBLE FLUIDS WITH VACUUM

  • Cho, Yong-Geun;Kim, Hyun-Seok
    • Journal of the Korean Mathematical Society
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    • v.45 no.3
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    • pp.645-681
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    • 2008
  • The Navier-Stokes system for heat-conducting incompressible fluids is studied in a domain ${\Omega}{\subset}R^3$. The viscosity, heat conduction coefficients and specific heat at constant volume are allowed to depend smoothly on density and temperature. We prove local existence of the unique strong solution, provided the initial data satisfy a natural compatibility condition. For the strong regularity, we do not assume the positivity of initial density; it may vanish in an open subset (vacuum) of ${\Omega}$ or decay at infinity when ${\Omega}$ is unbounded.

AN EFFICIENT INCOMPRESSIBLE FREE SURFACE FLOW SIMULATION USING GPU (GPU를 이용한 효율적인 비압축성 자유표면유동 해석)

  • Hong, H.E.;Ahn, H.T.;Myung, H.J.
    • Journal of computational fluids engineering
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    • v.17 no.2
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    • pp.35-41
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    • 2012
  • This paper presents incompressible Navier-Stokes solution algorithm for 2D Free-surface flow problems on the Cartesian mesh, which was implemented to run on Graphics Processing Units(GPU). The INS solver utilizes the variable arrangement on the Cartesian mesh, Finite Volume discretization along Constrained Interpolation Profile-Conservative Semi-Lagrangian(CIP-CSL). Solution procedure of incompressible Navier-Stokes equations for free-surface flow takes considerable amount of computation time and memory space even in modern multi-core computing architecture based on Central Processing Units(CPUs). By the recent development of computer architecture technology, Graphics Processing Unit(GPU)'s scientific computing performance outperforms that of CPU's. This paper focus on the utilization of GPU's high performance computing capability, and presents an efficient solution algorithm for free surface flow simulation. The performance of the GPU implementations with double precision accuracy is compared to that of the CPU code using an representative free-surface flow problem, namely. dam-break problem.

Higher Order Wall Boundary Conditions for Incompressible Flow Simulations

  • Nishida Hidetoshi
    • 한국전산유체공학회:학술대회논문집
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    • pp.61-62
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    • 2003
  • In this paper, the new higher order wall boundary conditions are proposed for solving the incompressible flows. The square driven cavity flows are simulated by using the variable order method of lines with the present wall boundary conditions. The variable order method of lines is constructed by the spatial discretization, i.e., the variable order proper convective scheme for convective terms and the modified differential quadrature method for diffusive terms, and time integration. The 2nd, 4th, and 6th order solutions are presented and these results show this higher order boundary conditions are very promising for the incompressible flow simulations.

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Incompressible Viscous Analysis on Unstructured Meshes using Artificial Compressibility Method (가압축성 기법을 이용한 비정렬 격자상에서의 비압축성 점성해석)

  • Moon Young J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.113-117
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    • 1995
  • Viscous analysis on incompressible flows is performed using unstructured triangular meshes. A two-dimensional and axisymmetric incompressible Navier-Stokes equations are solved in time-marching form by artificial compressibility method. The governing equations are discretized by a cell-centered based finite-volume method. and a centered scheme is used for inviscid and viscous fluxes with fourth order artificial dissipation. An explicit multi-stage Runge-Kutta method is used for the time integration with local time stepping and implicit residual smoothing. Convergence properties are examined and solution accuracies are also validated with benchmark solution and experiment.

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Development of an Incompressible Navier-Stokes Solver using SMAC Algorithm on Unstructured Triangular Meshes (비구조형 삼각형 격자에 대한 SMAC기법을 이용한 비압축성 나비어-스톡스 방정식 해법 개발)

  • Nam Hyeun S.;Moon Young J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.55-60
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    • 1997
  • An unstructured finite volume method is presented for seeking steady and unsteady flow solutions of the two-dimensional incompressible viscous flows. In the present method, SMAC-type algorithm is implemented on unstructured triangular meshes, using second order upwind scheme for the convective fluxes. Validation tests are made for various steady and unsteady incompressible flows. Convergence characteristics are examined and accuracy comparisons are made with some benchmark solutions.

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