• Title/Summary/Keyword: Flux-difference splitting

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Computation of the Euler Equations on the Adaptive Cartesian Grids Using the Point Gauss-Seidel Method (적응형 Cartesian 격자기법에서 Point Gauss-Seidel 기법을 사주한 Euler 방정식 계산)

  • Lee J. G.;Chang K. S.
    • 한국전산유체공학회:학술대회논문집
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    • 2001.05a
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    • pp.93-98
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    • 2001
  • An adaptive Cartesian grid method having the best elements of structured, unstructured, and Cartesian grids is developed to solve the steady two-dimensional Euler equations. The solver is based on a cell-centered finite-volume method with Roe's flux-difference splitting and implicit point Gauss-seidel time integration method. Calculations of several compressible flows are carried out to show the efficiency of the developed computer code. The results were generally in good agreements with existing data in the literature and the developed code has the good ability to capture important feature of the flows.

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Turbulent flow fields analysis using CFDS scheme (CFDS기법을 이용한 난류 유동장 해석)

  • Moon S. M.;Lee J. S.;Kim C.;Rho O. H.;Hong S. K.
    • 한국전산유체공학회:학술대회논문집
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    • 2001.05a
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    • pp.51-59
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    • 2001
  • An evaluation of one zero-equation and two one-equation eddy viscosity-transport turbulence closure models as implemented CFDS(Characteristic Flux Difference Splitting ) code is presented herein. Comparisons of Baldwin-Lomax model as zero-equation and Baldwin-Barth and Spalart-Allmaras model as one-equation are presented for three test cases, first inlvolving the 3 dimensional supersonic flow at M=1.98 over tangent ogive cylinder, second involving the 2 dimensional transonic flow at M=0.79 over RAE 2822 airfoil, third involving the 3 dimensional transonic flow at M=0.84 over ONERA M6 wing. The numerical results of CFDS code will also examined through direct comparison with experimental data.

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Assessment of Rotor Hover Performance Using a Node-based Flow Solver

  • Jung, Mun-Seung;Kwon, Oh-Joon;Kang, Hee-Jung
    • International Journal of Aeronautical and Space Sciences
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    • v.8 no.2
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    • pp.44-53
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    • 2007
  • A three-dimensional viscous flow solver has been developed for the prediction of the aerodynamic performance of hovering helicopter rotor blades using unstructured hybrid meshes. The flow solver utilized a vertex-centered finite-volume scheme that is based on the Roe's flux-difference splitting with an implicit Jacobi/Gauss-Seidel time integration. The eddy viscosity are estimated by the Spalart- Allmaras one-equation turbulence model. Calculations were performed at three operating conditions with varying tip Mach number and collective pitch setting for the Caradonna-Tung rotor in hover. Additional computations are made for the UH-60A rotor in hover. Reasonable agreements were obtained between the present results and the experiment in both blade loading and overall rotor performance. It was demonstrated that the present vertex-centered flow solver is an efficient and accurate tool for the assessment of rotor performance in hover.

A numerical study on the chemically reacting flow at highly altitude (고 고도에서의 화학적 변화를 수반하는 기체 유동에 대한 수치해석적 연구)

  • 이진호;김현우;원성연
    • Journal of the Korea Institute of Military Science and Technology
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    • v.4 no.2
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    • pp.202-214
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    • 2001
  • In this paper the upwind flux difference splitting Navier-Stokes method has been applied to study quasi one-dimensional nozzle flow and axisymmetric sphere-cone($5^{\circ}$) flow for the perfect gas, the equilibrium and the nonequilibrium chemically reacting hypersonic flow. The effective gamma(${ \tilde{\gamma}}$), enthalpy to internal energy ratio was used to couple chemistry with the fluid mechanics for equilibrium chemically reacting air. The influences of the various altitude(30km, 50km) at Mach number(15.0, 20.0) were investigated. The equilibrium shock position was located farthest downstream when compared with those of perfect gas in a quasi one-dimensional nozzle. The equilibrium shock thickness over the blunt body region was much thinner than that of perfect gas shock.

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Implicit Incompressible flow solver on Unstructured Hybrid grids (비구조 혼합 격자에서 내재적 방법을 이용한 비압축성 유동해석)

  • Kim J.;Kim Y.M;Maeng J.S
    • 한국전산유체공학회:학술대회논문집
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    • 1998.11a
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    • pp.48-54
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    • 1998
  • Three-dimensional incompressible Navier-Stokes equations have been solved by the node-centered finite volume method with unstructured hybrid grids. The pressure-velocity coupling is handled by the artificial compressibility algorithm and convective fluxes are obtained by Roe's flux difference splitting scheme with linear reconstruction of the solutions. Euler implicit method is used for time-integration. The viscous terms are discretised in a manner to handle any kind of grids such as tetrahedra, prisms, pyramids, hexahedra, or mixed-element grid. The numerical efficiency and accuracy of the present method is critically evaluated for several example problems.

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A NUMERICAL STUDY OF FLOWFIELD AT A SUPERSONIC INLET BY CHANGING ANGLES OF ATTACK AND CHANNEL LENGTH (초음속 흡입구의 통로길이와 받음각에 따른 유동장 변화 연구)

  • Ryu, K.J.;Lim, S.;Kim, S.D.;Song, D.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.21-27
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    • 2010
  • The flow characteristics on a supersonic inlet with bleeding system by changing angles of attack and channel length conditions are studied by computational 3D turbulent flow analysis. A compressible upwind flux difference splitting Navier-Stokes method with $k-{\omega}$ turbulence model is used to analysis the inlet flowfield. More non-uniform flowfields are shown at the AIP when angle of attack becomes bigger and bigger. These non-uniform flowfield works the performance aggravating factors of the supersonic engine. Non-uniform flowfield by changing channel length at the various angle of attack are investigated.

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IMPLEMENTATION OF FULL WEB-BASED GRAPHIC USER INTERFACE PROCESSOR FOR CFD SOFTWARE (웹 기반 CFD s/w용 GUI 프로세서의 구현)

  • Juraeva Makhsuda;Ivanov Evgeny G.;Song Dong Joo
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.121-125
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    • 2004
  • The preprocessor - solver - postprocessor software for 2D/Axisymmetric CSCM Upwind Flux Difference Splitting Navier-Stokes code has been developed for undergraduate educational purpose. This computational fluid dynamics (CFD) software allows students to setup, solve, visualize and control dynamically server for their own fluid problems via Internet. The preprocessor Is capable of generating geometry and grid, initial solution data and required solver control parameters. The postprocessor shows vector plot and contour plot with different options while residual plot shows root-mean-square (RMS) error history graphically and retrieves the data from solver interactively. Special feature of the preprocessor is grid generation part which is based on MFC/Visual C++ application and FORTRAN single block grid generator process. Many users can access solver via Internet from client computers and solve desired problems using locally installed pre- and postprocessor and remote powerful solver part.

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Numerical study of CEDS scheme for turbulent flow (난류 유동장에 대한 CFDS 기법의 수치적 연구)

  • Moon Seong Mok;Kim Chongam;Rho Oh Hyun;Hong Seung Kyu
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.23-26
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    • 2002
  • An evaluation of one algebraic and two one-equation eddy viscosity-transport turbulence closure models as implemented to the CFDS(Characteristic Flux Difference Splitting) scheme is presented for the efficient computation of the turbulent flow. Comparisons of Baldwin-Lomax model as algebraic turbulence model and Baldwin-Barth and Spalart-Allmaras model as one-equation turbulence model are presented for three test cases for 3-dimensional flow. The numerical result of the CFDS schem is examined through comparison with the experimental data.

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A Numerical Study on Efficiency and Convergence for Various Implicit Approximate Factorization Algorithms in Compressible Flow Field. (다양한 근사인수분해 알고리즘을 이용하여 압축성 유동장의 수렴성 및 유용성에 대한 연구)

  • Gwon Chang-O;Song Dong-Ju
    • 한국전산유체공학회:학술대회논문집
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    • 1999.11a
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    • pp.17-22
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    • 1999
  • Convergence characteristics and efficiency of three implicit approximate factorization schemes(ADI, DDADI and MAF) are examined using 2-Dimensional compressible upwind Navier-Stokes code. Second-order CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method with Fromm scheme is used for the right-hand side residual evaluation, while generally first-order upwind differencing is used for the implicit operator on the left-hand side. Convergence studies are performed using an example of the flow past a NACA0012 airfoil at steady transonic flow condition, i. e. Mach number 0.8 at $1.25^{\circ}$ angle of attack. The results were compared with other computational results in order to validate the current numerical analysis. The results from the implicit AF algorithms were compared well in low surface with the other computational results; however, not well in upper surface. It might be due to lack of the grid around the shock position. Because the algorithm minimizes the errors of the approximate decomposition, the improved convergence rate with MAF were observed.

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Aerodynamic Calculations in Hover of KUH Rotor Blade (한국형 기동헬기 블레이드의 제자리 비행 공력 해석)

  • Kang, Hee-Jung;Kim, Seung-Ho;Jung, Mun-Seung;Lee, Hee-Dong;Kwon, Oh-Joon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.25-28
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    • 2008
  • An aerodynamic calculation in hover of KUH main rotor blade is performed using a three-dimensional unstructured hybrid mesh viscous flow solver. The flow solver utilizes a vertex-centered finite-volume scheme that is based on the Roe's flux-difference splitting with an implicit Jacobi/Gauss-Seidel time integration. The eddy viscosity are estimated by the Spalart-Allmaras one-equation turbulence model. A solution-adaptive mesh refinement technique is used for efficient capturing of the tip vortex. Calculations are performed at several operating conditions with varying collective pitch setting for KUH main rotor blade in hover. Good agreements are obtained between the present and other results using HOST and CAMRAD II in overall rotor performance. It is demonstrated that the present vertex-centered flow solver is an efficient and accurate tool for the assessment of rotor performance in hover.

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