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  • 1
    Electronic Resource
    Electronic Resource
    Preconditioned conjugate gradient methods for three-dimensional linear elasticity (1994)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 2211-2234 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite element modelling of three-dimensional elasticity problems give rise to large sparse matrices. Various preconditioning methods are developed for use in preconditioned conjugate gradient iterative solution techniques. Incomplete factorizations based on levels of fill, drop tolerance, and a two-level hierarchical basis are developed. Various techniques for ensuring that the incomplete factors have positive pivots are presented. Computational tests are carried out for problems generated using unstructured tetrahedral meshes. Quadratic basis functions are used. The performance of the iterative methods is compared to a standard direct sparse matrix solver. Problems with up to 70 000 degrees of freedom and small (≪1) element aspect ratio are considered.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620371305
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  • 2
    Electronic Resource
    Electronic Resource
    A two-phase, two-component model for natural convection in a porous medium (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 655-682 
    Details
    ISSN: 0271-2091
    Keywords: Two-phase ; Porous medium ; Convection ; Heat pipe ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical study of natural convection in a two-phase, two-component flow in a porous medium heated from below is presented. Interphase mass and energy transfer, latent heat and bouyancy effects are major physical features. This study extends earlier studies of natural convection based on single-phase, saturated porous medium models. The appearance of two-phase heat pipe zones in the flow has a marked effect on the fluid and heat flows as well as on the performance of the numerical methods. The numerical techniques for handling phase change, Jacobian construction and time step selection are discussed.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650120705
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  • 3
    Electronic Resource
    Electronic Resource
    Preconditioned conjugate gradient methods for the incompressible Navier-Stokes equations (1992)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 15 (1992), S. 273-295 
    Details
    ISSN: 0271-2091
    Keywords: Navier-Stokes ; ILU(l) ; Preconditioned conjugate gradient ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A robust technique for solving primitive variable formulations of the incompressible Navier-Stokes equations is to use Newton iteration for the fully implicit non-linear equations. A direct sparse matrix method can be used to solve the Jacobian but is costly for large problems; an alternative is to use an iterative matrix method. This paper investigates effective ways of using a conjugate-gradient-type method with an incomplete LU factorization preconditioner for two-dimensional incompressible viscous flow problems. Special attention is paid to the ordering of unknowns, with emphasis on a minimum updating matrix (MUM) ordering. Numerical results are given for several test problems.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650150303
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  • 4
    Electronic Resource
    Electronic Resource
    Three-dimensional modelling of steam flush for DNAPL site remediation (1994)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 19 (1994), S. 1055-1081 
    Details
    ISSN: 0271-2091
    Keywords: Multiphase porous media flow ; Primary variable selection ; Horizontal wells ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Numerical simulation of steam flush for clean-up of non-aqueous phase liquid (NAPL) contaminated groundwater sites involves solution of the multiphase, multicomponent subsurface flow equations. This paper describes techniques for discretizing problems with horizontal wells in a three-dimensiontetrahedral mesh. The effectiveness of non-linear flux limiters for reducing numerical dispersion is discussed. Primary variable selection and thermodynamic state transition rules will also be compared. Some example results for several steam flush scenarios will be presented.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650191202
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  • 5
    Electronic Resource
    Electronic Resource
    A control volume finite element method for three-dimensional NAPL groundwater contamination (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 13 (1991), S. 955-970 
    Details
    ISSN: 0271-2091
    Keywords: Three-dimensional tetrahedral ; NAPL contamination ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A three-dimensional control volume finite element method is developed for NAPL groundwater contamination problems. Tetrahedral elements are formed by decomposing deformed blocks. The decomposition is carried out in such a way as to minimize the size of the negative transmissibilities. Negative transmissibilities produce non-physical discrete fluid flow paths and can cause oscillatory behaviour in the Newton iteration. Example results are presented for a three-dimensional NAPL contamination scenario using typical geophysical data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650130803
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