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  • Digitale Medien  (14.344)
  • Engineering General  (9.884)
  • Nuclear reactions  (4.460)
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  • Digitale Medien  (14.344)
Erscheinungszeitraum
  • 101
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 135-140 
    ISSN: 1069-8299
    Schlagwort(e): finite elements ; QUAD4 elements ; RBF corrections ; shear force predictions ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The residual bending flexibility correction is an extra-variational trick used to enhance the convergence rate of shear flexible beam and plate elements. In the paper we show how this can affect the shear deflection and shear force estimates in the QUAD4 element.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 102
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 141-145 
    ISSN: 1069-8299
    Schlagwort(e): numerical integration ; Gauss quadrature rules ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The advance of powerful software for symbolic and numerical computations such as Mathematica sheds a new light on a paper by Golub and Welsch from 1969. Based on this paper the author describes a Mathematica procedure for determining the weights and abscissae of a Gauss quadrature rule with a user-defined weight function. After a brief description of the algorithm and its implementation examples demonstrate the usefulness of the procedure. The procedure is extremely useful if one has to compute many integrals with the same, possibly weakly singular, weight function. This might happen, for example, in the boundary element method.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 103
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 331-341 
    ISSN: 1069-8299
    Schlagwort(e): glass ; finite element ; strategy's creep forming ; sheet ; manufacture ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An original optimization strategy for creep forming is carried out by finite element thermodependent viscoplastic models. For reference design glass products, an optimum forming database is developed in two steps: the first step analyses feasibility, with elastic and viscoplastic finite element models, with regard to initial manufacture choices. With thermodependent viscoplastic finite element models, the second step leads to optimum forming parameters, concerning skeleton bending radii and/or non-homogeneous heating adjustments.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 104
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 321-330 
    ISSN: 1069-8299
    Schlagwort(e): solid-shell structure ; 3D solid element ; degenerated shell element ; DOF expanding ; multipoint constraint equations ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper presents a degree of freedom expanding method for dealing with the connections of 3D isoparametric solid elements and the degenerated shell elements. By introducing two degrees of freedom to describe the elongation in the normal direction of the shell node linked with solid elements, a series of multipoint constraint equations which provide proper connections of solid and shell nodes are raised. The method gives a complete solution to the problem of connection between 3D isoparametric solid elements and degenerated shell elements even for the thermal elasto-plastic problem. It can adapt to complex junctions and simplify programming. Numerical examples are also presented to demonstrate the accuracy and feasibility in thermal elasto-plastic analysis.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 105
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 351-357 
    ISSN: 1069-8299
    Schlagwort(e): anisotropy ; finite elements ; layers ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A modification of the usual quadrangle (2D) and brick (3D) finite element for field problems is proposed. It allows the principal directions of the conductivity tensor (anisotropy directions) to be derived from the geometrical shape of the finite element and to change within it. An internal layering is assumed which is parallel to the boundary at two opposite faces (top and bottom) of the element. Without an explicit computation of angles the anisotropy directions are parallel and perpendicular to this layering. An application is the modelling of pore fluid flow in sedimentary basins.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 106
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 343-349 
    ISSN: 1069-8299
    Schlagwort(e): mesh generation ; Delaunay mesh ; Watsens method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Automated mesh generation using a combined octree/Delaunay approach typically requires that rectangular elements be bounded by other rectangular elements which are not more that one division smaller (i.e. 1/8 the volume in 3D). This limitation is sometimes referred to as the 2 : 1 rule. This paper presents a modification which allows for any level of difference.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 107
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996) 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 108
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 359-369 
    ISSN: 1069-8299
    Schlagwort(e): Navier-Stokes ; artificial compressibility methodology ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper considers the problem of laminar incompressible viscous flow through a wavy channel. An artificial compressibility method using the approximate factorization technique is applied to solve the velocity-pressure formulation of the Navier-Stokes equations written in curvilinear non-orthogonal coordinates. The physical domain used was one wavelength of the channel in which appropriate periodicity conditions were applied in order to find a solution independent of entry effects. Flow separation was observed for high Re numbers and/or large wave amplitudes of the channel. The effect of inertia to the velocity profiles was observed, and pressure and shear stress were calculated along the length of the channel. These flows have great interest in industry and medicine such as for the extracorporeal membrane oxygenator.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 109
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 445-446 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 110
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 483-495 
    ISSN: 1069-8299
    Schlagwort(e): finite element method ; solid modelling ; optimal interpolation ; a posteriori error estimation ; adaptive interpolation ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The problem of approximating functions is considered in a general domain in one and two dimensions using piecewise polynomial interpolation. An error estimator is proposed which shows how to adaptively determine the interpolation degree. Numerical examples are given.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 111
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 461-470 
    ISSN: 1069-8299
    Schlagwort(e): linear polyhedra ; symbolic integration ; polynomial functions ; monomials ; tetrahedron ; hexahedron ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper concerns analytical integration of polynomial functions over linear polyhedra in three-dimensional space. To the authors' knowledge this is a first presentation of the analytical integration of monomials over a tetrahedral solid in 3D space. A linear polyhedron can be obtained by decomposing it into a set of solid tetrahedrons, but the division of a linear polyhedral solid in 3D space into tetrahedra sometimes presents difficulties of visualization and could easily lead to errors in nodal numbering, etc We have taken this into account and also the linearity property of integration to derive a symbolic integration formula for linear hexahedra in 3D space. We have also used yet another fact that a hexahedron could be built up in two, and only two, distinct ways from five tetrahedral shaped elements These symbolic integration formulas are then followed by an illustrative numerical example for a rectangular prism element, which clearly verifies the formulas derived for the tetrahedron and hexahedron elements.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 112
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 497-505 
    ISSN: 1069-8299
    Schlagwort(e): weight function approach ; edge crack problem ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A fundamental field for the edge crack problem is suggested, and the field is composed of the singular displacement field and the complementary regular field. The boundary displacement of the fundamental field plays the role of the weight function in the edge crack problem. After multiplying the boundary traction in the physical problem with the weight function and performing integration along the boundary, the stress intensity factor at the crack tip is obtainable. Numerical examples are given to demonstrate the use of the suggested weight function approach.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 113
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 543-555 
    ISSN: 1069-8299
    Schlagwort(e): control volume method ; finite element interpolation ; fluid flow ; upwind schemes ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Together with the finite element method (FEM), the control volume method (CVM) is of particular interest for the numerical solution of partial differential equations. The accuracy of computation of the CVM almost matches that of FEM in contour-adapted co-ordinates or block-structured meshes of a single element type. The CVM is superior to the FEM in terms of physical interpretation and ease of handling. The paper presents an interpretation of the FEM that allows it to be treated like a CVM. This formal CVM, which is based on FEM techniques, combines the advantages of both methods. The method is applied to the discretization of the Navier-Stokes equation.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 114
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 557-568 
    ISSN: 1069-8299
    Schlagwort(e): hyperbolic equations ; finite-difference methods ; Padé approximants ; sequential and parallel implementation ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Techniques for two-time level difference schemes are presented for the numerical solution of first-order hyperbolic partial differential equations. The space derivative is approximated by (i) a low-order, and (ii) a higher-order backward difference replacement, resulting in a system of first-order ordinary differential equations, the solutions of which satisfy recurrence relations. The methods are obtained from the recurrence relations and are tested on three linear problems and one non-linear problem from the literature.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
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  • 115
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 507-517 
    ISSN: 1069-8299
    Schlagwort(e): non-linear constitutive model ; anisotropy ; finite strains ; axisymmetrical finite elements ; vascular biomechanics ; soft tissue biomechanics ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: To explore the mechanical non-linear behaviour of anisotropic arterial walls on a computational basis, the formulation of a continuum based elastic potential is a major task and challenge to the analyst. The present communication is concerned with the constitutive modelling and numerical analysis of vascular segments covering finite strains. Special attention is paid to a two term potential that constitutes an essential foundation for accurate simulation within the entire strain domain. Axisymmetrical membrane elements are assembled to match the geometry of blood vessels. Numerical results confirm the theoretical approach by referring to experimental data of different rat arteries.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 116
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 569-579 
    ISSN: 1069-8299
    Schlagwort(e): frictional contact ; large deformation ; one-pass approach ; master segment ; slave node ; contact constraint ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In the context of large deformation analysis for metal forming processes a new one-pass approach for the frictional contact is proposed. This approach eliminates the short comings of traditional one-pass and two-pass approaches both from the constraint requirement and solution convergence points of view. Implemented in an updated Lagrangian framework with the Perturbed Lagrangian formulation of Ju and Taylor for non-linear frictional contact, a patch test and typical examples have been worked out to prove the validity of the proposed approach. It is observed that a finer surface discretization of the slave and master surfaces is no longer needed to enforce contact constraint.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 117
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 673-682 
    ISSN: 1069-8299
    Schlagwort(e): temperature field ; heat source ; IBEM ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The fundamental solution of the temperature field in an infinite three-dimensional body under the periodic unit thermal source is given in the present paper. According to the indirect boundary element method (IBEM) with fictitious heat sources, the problem of 3-D periodic heat conduction in a finite body is solved. By use of a quadratic inharmonic element, the problem of the corner region and the indetermination of the normal direction at boundary points can be solved in the numerical process. The validity of the present method is checked with two examples of which analytical solutions exist. It offers a useful method for the actual simulated calculation of the 3-D temperature field in engineering.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 795-804 
    ISSN: 1069-8299
    Schlagwort(e): RLW equation ; finite element methods ; Petrov-Galerkin ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The RLW equation is solved by a least-squares technique using linear space-time finite elements. In simulations of the migration of a single solitary wave this algorithm is shown to have higher accuracy and better conservation than a recent difference scheme based on cubic spline interpolation functions. In addition, for very small amplitude waves (≤ 0.09) it has higher accuracy than an approach using quadratic B-spline finite elements within Galerkin's method. The development of an undular bore is modelled.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 119
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 787-793 
    ISSN: 1069-8299
    Schlagwort(e): regularization ; boundary integral equations ; hypersingular integrals ; Hadamard finite part ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Strongly singular integrals which are unbounded in the sense of Lebesgue appear naturally in boundary integral equations. Extending the analytic continuation method we derive finite part values for a class of singular integrals which arise frequently in practice. In connection with boundary integral operators we derive restrictions on the minimum smoothness of the density functions for the validity of the finite part results. Examples of applications of the results to boundary integral equations in potential theory are presented.
    Materialart: Digitale Medien
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  • 120
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996) 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 121
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 805-805 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 827-834 
    ISSN: 1069-8299
    Schlagwort(e): stress-strain relationship ; monotonic loading ; failure stress ; failure strain ; initial modulus ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A function containing four parameters allowing close approximation of experimental stress-strain relationships is presented. The parameters are easily determined from corresponding conditions at the ends and inside of the total interval of the strain variation from zero stain up to failure stain. The family of curves obtained covers an area on the stress-strain plane where any acceptable stress-strain curve can pass. The softening behaviour of soils can also be taken into consideration.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 123
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 807-826 
    ISSN: 1069-8299
    Schlagwort(e): incompressible materials ; finite element method ; p-version ; elasticity ; stress extraction ; complementary energy ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Direct methods for computing the pointwise stresses for nearly incompressible elastic materials fail to provide meaningful results when applied to the displacement formulation of the finite element method (FEM). A new extraction method for accurate computation of pointwise stresses for nearly incompressible elastic materials is presented. It is based on the complementary energy principle applied over a local domain in the postprocessing phase in conjunction with the p-version finite element solution. It is shown that accurate pointwise stresses are obtained, that the relative error in the pointwise stresses converges at a rate which is as fast as the relative error measured in the energy norm or faster, and importantly, the extracted stresses are virtually independent of Poisson's ratio. Numerical results for two problems, one having a smooth solution and the other containing a singular point, are provided.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 124
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 835-847 
    ISSN: 1069-8299
    Schlagwort(e): superposition method ; perturbation of eigenvectors ; structural modification ; basis ofN-dimension Euclidean space ; orthogonalization of Schmit procedure ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The modal superposition method is often used for computing the perturbation of eigenvectors in structural modification and model correction. However, it will bring about significant errors in the solution when the high-frequency modes are truncated. This paper presents a new method, which uses known modes construct a new basis of the N-dimensional Euclidean space (say, the mixed-basis), to calculate the first and second order perturbations of the known eigenvectors. In the present method only the known modes are used. The accuracy of this method not only has no relation to number of the truncated modes but is better than the truncated modal superposition method, in which only the known modes are employed. A numerical example of a truss structure with 36 degrees of freedom is given to illustrate the effectiveness of the method.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 125
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 849-862 
    ISSN: 1069-8299
    Schlagwort(e): superconvergence ; isoparametric bilinear finite elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this paper the superconvergence property of isoparametric bilinear finite elements is considered. A new superconvergence recovery method for isoparametric bilinear finite elements is discovered on the four vertices and the four midpoints of the edges of the elements for piecewise strongly regular quadrilateral subdivisions.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 126
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996) 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 127
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 873-884 
    ISSN: 1069-8299
    Schlagwort(e): thin-walled beam ; finite element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A new method for computing the deformation of thin-walled beams with closed cross-section under warping torsional loading is presented. In comparison to the classical theory (Umanski), the hypothesis of no deformation of the contour of the cross-section of the beam is maintained and the assumption of no distortion of the cross-section plane is modified. The new approach gives better results than the classical theory when both are compared to a standard finite element technique (using shell elements). The central idea of the new approach lies in the usage of a new finite element called a macro-element, which is especially well suited for thin-walled beam computations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 128
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 885-896 
    ISSN: 1069-8299
    Schlagwort(e): interfaces ; sliding ; contact ; impact ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper presents an automatic sliding interface algorithm for intense impulsive loading computations due to high velocity impact and explosive detonation. This algorithm allows the user to perform computations involving complex sliding interfaces without having to predetermine the sliding interfaces; everything is automated. The interface determination algorithm, the searching algorithm and the contact algorithm are included.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 129
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 863-871 
    ISSN: 1069-8299
    Schlagwort(e): objectivity ; kinematics ; computational mechanics ; large deformations ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this paper, an example problem is presented that illustrates the importance of strong objectivity in kinematic algorithms for large-deformation finite element applications. The example problem involves cyclic simple shearing of a hypoelastic material, wherein the increments of stretch and of rotation are of comparable magnitude. It is demonstrated that two kinematic algorithms that are in common use, and which are only weakly objective, give rise to an accumulative error in the normal stress components. The error is surprisingly large, even for very small strain increments. This behaviour arises due to a coupling between the stretch and rotation increments that is exhibited by weakly objective algorithms, and is perhaps especially serious in the context of models for jointed rock and other frictional materials, in which the shear response may depend strongly on the normal components of stress.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 130
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 905-905 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 131
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 95-105 
    ISSN: 1069-8299
    Schlagwort(e): generalized Helmholtz equation ; shape sensitivity analysis ; shape optimization ; boundary element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The present paper deals with the shape design optimization of bodies subjected to a non-homogeneous Helmholtz equation. Using the adjoint variable method the material derivative of a general integral functional is obtained analytically. Boundary integral equations defined only on the boundary are derived using auxiliary fundamental solutions to be used in the boundary element method. Some constrained shape design optimization problems are solved by the proposed numerical procedure.
    Zusätzliches Material: 5 Ill.
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  • 132
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 85-93 
    ISSN: 1069-8299
    Schlagwort(e): nearly singular kernel integrals ; curved boundary elements ; numerical integration ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper attempts to improve the efficiency of a general method developed previously for computing nearly singular kernel integrals. Three new formulations are presented by following an approach similar to that used in the previous method. Their numerical efficiency is compared with the previous method. The results indicate that these new formulations are substantially more efficient than the previous method. In particular, the new formulation in which the same sampling points for all n values are used is the most efficient. This new formulation remains highly efficient even when the field point is as close to the panel surface as 0·1 per cent of the panel diagonal.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 133
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 127-134 
    ISSN: 1069-8299
    Schlagwort(e): Laplace equation ; singularities ; boundary integral method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The authors present a new singular function boundary integral method for the numerical solution of problems with singularities which is based on approximation of the solution by the leading terms of the local asymptotic expansion. The essential boundary conditions are weakly enforced by means of appropriate Lagrange multipliers. The method is applied to a benchmark Laplace-equation problem, the Motz problem, giving extremely accurate estimates for the leading singular coefficients. The method converges exponentially with the number of singular functions and requires a low computational cost. Comparisons are made to the analytical solution and other numerical methods.
    Zusätzliches Material: 4 Ill.
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  • 134
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 115-125 
    ISSN: 1069-8299
    Schlagwort(e): experimental measurements ; filtering ; dynamics ; structures ; models ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper presents a filtering algorithm which corrects the results of measurements of certain physical quantities if some information about the model of the system is known. The results of measurements are not only obtained in an explicit form for the considered variable but also in a form of dependent variables which are related to the measured quantity by certain mathematical relations. Combining the information obtained from different measurements, much better accuracy can be reached. It is proved that the proposed algorithm is able not only to enhance the measured data but also to detect the errors of the instruments.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 135
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996) 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 136
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 221-222 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 137
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 151-159 
    ISSN: 1069-8299
    Schlagwort(e): response reanalysis ; structural modifications ; matrix partitioning ; Sherman-Morrison formula ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper lays out an exact method, using the receptance strategy, to calculate the frequency response of a modified structure. A direct inversion of the modified impedance matrix is proposed, which reduces the computation time for successive calculations of an evolving design of the structure.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 138
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 175-180 
    ISSN: 1069-8299
    Schlagwort(e): permanent capillar-heavy waves ; conformal mapping ; circular shaped channels ; Zeidler's method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: E. Zeidler gave an existence and uniqueness proof for permanent heavy and capillar-heavy waves in circular shaped channels. Based on this proof and on a general computational method for constructing the solutions numerically given by the author (1991), the case of permanent heavy waves in circular shaped channels was recently computed by the author. In this work the case of permanent capillar-heavy waves in circular shaped channels is considered.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 139
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 161-173 
    ISSN: 1069-8299
    Schlagwort(e): inverse identification ; non-linear behaviour ; material parameters ; sensitivity analysis ; finite elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The identification of materials rheological behaviour in the non-linear range is based on experimental tests. When using direct identification methods, one faces the problem of the interpretation of the experimental tests, which requires the assumption of deformation homogeneity and therefore the use of approximation methods. Since this assumption is often not satisfied in the case of non-linear behaviour, material parameters are not assessed precisely. In the paper, an inverse identification method is proposed to avoid the problems raised by interpretation of the experimental tests and to determine material parameters more accurately. The algorithm developed consists of both an optimization method and a finite element method. This method is applied to the inverse identification of viscoplastic parameters of an aluminium alloy, with an investigation on the effect of the initial guess and errors in experimental data on the identified values.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 140
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 181-184 
    ISSN: 1069-8299
    Schlagwort(e): finite elements ; infinite elements ; mapping functions ; unbounded domains ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A few of the published three-dimensional Serendipity infinite element mapping functions have been discovered to be in error. The paper gives corrected versions of the defective mapping functions. The problems only relate to three-dimensional elements of the Serendipity type, when they extend to infinity in two or more directions. The new version of the mapping functions have been tested and appear to be robust.
    Zusätzliches Material: 3 Tab.
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  • 141
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 269-270 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 142
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 209-220 
    ISSN: 1069-8299
    Schlagwort(e): boundary element method ; dual reciprocity ; radial basis functions ; augmented thin plate splines ; body forces ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper presents a novel dual reciprocity formulation for elasticity problems with body forces in which the approximating functions are given in terms of augmented thin plate splines (ATPS). It is shown that the ATPS approximation is capable of correctly representing gravitational and centrifugal body forces, and provides superior accuracy for general load cases.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 143
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 197-208 
    ISSN: 1069-8299
    Schlagwort(e): curved surface ; triangular mesh ; automatic generation ; Bézier patches ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper deals with the discretization of any given multi-connected curved surface into triangular elements with straight sides. The method evolves from an initial rough triangular mesh generated from a set of input points which describe the geometry of the problem domain. Interior nodes are distributed according to user-established node-spacing functions of pre-specified spacing control parameters, and they are linked using the advancing front technique. Particular attention is paid to obtaining good distribution of interior nodes in the vicinity of the domain limits. Surface geometry representation is established using triangular Bézier patches with G1 continuity. This approach ensures a geometrically well-defined working platform for the subsequent discretization of the problem domain. The proposed method requires minimum input from the user and allows mesh gradation and remeshing to be carried out in a straightforward manner. Furthermore, problems associated with variations in the domain geometry as a result of local remeshing are eliminated with the aid of the geometrically pre-defined discretization platform. Results are presented for a range of both curved and planar surfaces, typical of those which might be encountered in hydrodynamics modelling involving flows with a free surface. The presented results demonstrate the flexibility and power of the technique.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 144
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996) 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 145
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 75-76 
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 146
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 13-20 
    ISSN: 1069-8299
    Schlagwort(e): open channel flows ; Riemann solver ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An efficient numerical method is developed for the one-dimensional open channel flow equations. The scheme is a modification of one presented recently, but with an improvement in the efficiency made through the use of the arithmetic mean as an average of flow variables across the interface between adjacent states. Numerical results are shown for two problems, and an indication of the efficiency gained is given.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 147
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 1-11 
    ISSN: 1069-8299
    Schlagwort(e): interval parameters ; interval static responses ; interval linear equations ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A structure subjected to interval parameters and interval loads which are unknown, except for the fact that they belong to given intervals, is studied and the displacement bound estimation is given. These parameters are uncertain, and yet they are not treated as being random since no information is available on their probabilistic characteristics. A set of possible states of the system is described by interval matrices. The perturbation method is employed as a simple analytical tool for determining static responses - interval displacements of finite element equilibrium equations with interval parameters. The numerical results show that the proposed method is extremely effective.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 148
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 21-29 
    ISSN: 1069-8299
    Schlagwort(e): finite element systems ; elliptic partial differential equations ; approximate LU factorization ; explicit matrix inversion ; preconditioning ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A new class of explicit generalized approximate inverse finite element matrix algorithmic methods, based on the concept of LU-sparse factorization procedures, without inverting the decomposition factors, has recently been introduced. The large sparse unsymmetric coefficient matrix of irregular structure is factorized approximately and, in conjunction with approximate inverse matrix techniques, yields explicit preconditioned methods for the finite element (FE) and finite difference (FD) method. The numerical implementation of these algorithms is presented and Fortran subroutines for the efficient solution of the sparse unsymmetric linear systems are given.
    Zusätzliches Material: 1 Tab.
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  • 149
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 31-42 
    ISSN: 1069-8299
    Schlagwort(e): explicit scheme ; implicit scheme time-stepping ; acceleration ; Chebyshev parabolic ; heat equation ; Stefan problem ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The goal of the paper is to bring to the attention of the computational community a long overlooked, very simple, acceleration method that impressively speeds up explicit time-stepping schemes, at essentially no extra cost. The authors explain the basis of the method, namely stabilization via wisely chosen inner steps (stages), justify it for linear problems, and spell out how simple it is to incorporate in any explicit code for parabolic problems. Finally, we demonstrate its performance on the (linear) heat equation as well as on the (non-linear) classical Stefan problem, by comparing it with standard implicit schemes (employing SOR or Newton iterations). The results show that super-time-stepping is more efficient than the implicit schemes in that it runs at least as fast, it is of comparable or better accuracy, and it is, of course, much easier to program (and to parallelize for distributed computing).
    Zusätzliches Material: 1 Ill.
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  • 150
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Linear Algebra with Applications 3 (1996), S. 525-542 
    ISSN: 1070-5325
    Schlagwort(e): potential flow problem in porous media ; mixed-hybrid formulation trilateral prismatic elements ; symmetric indefinite linear systems ; minimal residual method ; rate of convergence ; asymptotic convergence factor ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik
    Notizen: In the paper the potential fluic flow problem in porous media using Darcy's law and the continuity equation is solved. Mixed-hybrid finite element formulation based on general trilateral prismatic elements is considered. Spectral properties of resulting symmetric indefinite system of linear equations are examined. Minimal residual method for the solution of systems with a symmetric indefinite matrix is applied. The rate of convergence and the asymptotic convergence factor which depend on the eigenvalue distribution of the system matrix are estimated.
    Zusätzliches Material: 2 Ill.
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  • 151
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 939-949 
    ISSN: 0029-5981
    Schlagwort(e): adaptive grid ; recursive subdivision ; error reduction ; theoretic speedup ; efficient data structure ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Dynamic mesh adaptation is a very useful technique for reducing the computational time and memory requirements when solving evolutionary partial differential equations. The reduction is greater when the solution exhibits localized behaviour as in the case of a moving front where the ‘action’ occurs over a small fraction of the domain. Difficulties arising in the use of dynamic grid adaptation include significant overhead, added storage, and errors introduced due to grid manipulation. We propose a method that maintains a fine uniform grid in the important regions of the domain by using inexpensive action indicators to trigger selective refinement. The method is simple to code and adapt to existing finite element solvers. It requires low added storage and overhead per element, and can significantly reduce grid manipulation errors. We present the selective refinement method and its use of the solution in the gridding decision process, and detail the streamlined storage structure. Theoretical speedup compared to fixed grid methods is derived and the improvement in storage is analysed. Finally, we use the method to solve some problems exhibiting localized behaviour in one dimension and compare to theory.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 152
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 1261-1263 
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 153
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 1237-1258 
    ISSN: 0029-5981
    Schlagwort(e): differential quadrature method ; numerical solution methods ; higher-order partial differential equations ; multiple boundary conditions ; free vibration ; rectangular plates ; thin plate theory ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In the context of the free vibration problem of rectangular plates, this paper develops a detailed methodology for implementing multiple boundary conditions in the differential quadrature solutions of higher-order differential equations. It is explained that a certain type of boundary conditions can be built into the differential quadrature weighting coefficients themselves. This simplifies the programming of the differential quadrature solution algorithms. More importantly, however, as shown by the results of fundamental frequencies of a wide spectrum of rectangular plate configurations, the methodology results in strikingly accurate differential quadrature solutions.
    Zusätzliches Material: 1 Ill.
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  • 154
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 1264-1264 
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
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  • 155
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 393-409 
    ISSN: 0271-2091
    Schlagwort(e): generalized Stokes problem ; Chebyshev spectral method ; thermosolutal convection ; directional solidification ; vertical Bridgman problem ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The paper presents a Chebyshev-Fourier collocation method for solving the unsteady 3D Navier-Stokes equations in a cylindrical domain. The numerical scheme uses primitive variables and the incompressibility constraint is satisfied by applying iteratively a correction to the pressure field. The method, due to Cahouët and Chabard (Int. j. numer. methods fluids,8, 869-895 (1988)) and originally developed in the framework of finite elements, is checked with respect to the present high-order approach. Several tests are carried out in Cartesian geometries, successively 2D and 3D, then a comparison is performed in a cylindrical domain with two different sets of radial collocation nodes: Gauss-Lobatto nodes and Gauss-Radau points. Although quite acceptable results are obtained with the latter chain, a general decrease in efficiency is noticeable in the collocation method. This is interpreted as the consequence of two factors: the collocation formulation is not symmetric and the Fourier analysis, used as heuristic guide by CahouMt and Chabard, loses its efficiency in a non-equidistant grid, especially in a cylindrical geometry.We present an application to the study of thermosolutal convection induced by unidirectional solidification of a binary alloy. The latter grows from a Pb-30%Tl liquid phase in a cylindrical crucible corresponding to the vertical Bridgman upward configuration. We study the influence of the flow patterns on the crystal composition.
    Zusätzliches Material: 7 Ill.
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  • 156
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 447-448 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 157
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 11-27 
    ISSN: 0271-2091
    Schlagwort(e): finite elements ; liquid crystal ; nematic ; anisotropic ; electro rheological ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The orientation tensor L is introduced to construct a modified Leslie-Ericksen model for the viscous, incompressible flow of anisotropic suspensions (including electric field effects). This is then utilized to develop a weak variational formulation and finite element scheme for computing the flow and orientation fields. Numerical results are presented for exploratory test problems.
    Zusätzliches Material: 11 Ill.
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  • 158
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 1-9 
    ISSN: 0271-2091
    Schlagwort(e): 2D Navier- ; Stokes equations ; convergence under highRe ; homotopy ; BEM ; FDM ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In this paper the high-order formulations described by Liao (Int. j. numer. methods fluids, 15, 595-612 (1992)) are proved to be stable for viscous flow under high Reynolds number. As an example, results for shear-driven flow in a square cavity at Reynolds numbers up to 10,000 are given.
    Zusätzliches Material: 9 Ill.
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  • 159
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 619-641 
    ISSN: 0271-2091
    Schlagwort(e): convective transport ; monotonicity ; finite volume ; boundary-fitted co-ordinates ; turbulence modelling ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A formally third-order accurate finite volume upwind scheme which preserves monotonicity is constructed. It is based on a third-order polynomial interpolant in Leonard's normalized variable space. A flux limiter is derived using the fact that there exists a one-to-one map between normalized variable and TVD spaces. This scheme, which is relatively simple and quite compact, is implemented in a staggered general co-ordinates finite volume algorithm including the standard k-ε model and applied to the turbulence transport equations. A number of test problems demonstrate the utility of the proposed scheme. It is shown that in cases where turbulence convection is dominant, the application of a higher-order monotone convection scheme to the turbulence equations leads to results which are more accurate than those obtained using the first-order upwind scheme.
    Zusätzliches Material: 21 Ill.
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  • 160
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 731-754 
    ISSN: 0271-2091
    Schlagwort(e): thermally expandable flow ; covolume method ; characteristic curve ; Delaunay tessellation ; dual variable method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Finite-difference-like discretizations are developed for the time-dependent Navier-Stokes equations and the thermal energy equation on Delaunay triangulations of the flow domain. The flow is assumed to be thermally expandable; that is, the density varies only with temperature. A characteristic- like (CL) method is used to discretize the temporal and convective terms. The dual variable method reduces the size of the discrete system by a factor of five.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
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  • 161
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 353-373 
    ISSN: 0271-2091
    Schlagwort(e): Navier-Stokes equations ; finite differences ; unsymmetric linear systems ; Krylov subspace methods ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In many popular solution algorithms for the incompressible Navier-Stoke equations the coupling between the momentum equations is neglected when the linearized momentum equations are solved to update the velocities. This is known to lead to poor convergence in highly swirling flows where coupling between the radial and tangential momentum equations is strong. Here we propose a coupled solution algorithm in which the linearized momentum and continuity equations are solved simultaneously. Comparisons between the new method and the well-known SIMPLEC method are presented.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
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  • 162
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 411-428 
    ISSN: 0271-2091
    Schlagwort(e): composite grids ; adaptive grids ; multigrid parallelization ; Euler ; implicit scheme ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A method capable of solving very fast and robust complex non-linear systems of equations is presented. The block adaptive multigrid (BAM) method combines mesh adaptive techniques with multigrid and domain decomposition methods. The overall method is based on the FAS multigrid, but instead of using global grids, locally enriched subgrids are also employed in regions where excessive solution errors are encountered. The final mesh is a composite grid with uniform rectangular subgrids of various mesh densities. The regions where finer grid resolution is necessary are detected using an estimation of the solution error by comparing solutions between grid levels. Furthermore, an alternative domain decomposition strategy has been developed to take advantage of parallel computing machines. The proposed method has been applied to an implicit upwind Euler code (EuFlex) for the solution of complex transonic flows around aerofoils. The efficiency and robustness of the BAM method are demonstrated for two popular inviscid test cases. Up to 19-fold acceleration with respect to the single-grid solution has been achieved, but a further twofold speed-up is possible on four-processor parallel computers.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 163
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 467-481 
    ISSN: 0271-2091
    Schlagwort(e): centrifugal pump ; multidomain calculation ; unsteady flow ; finite volume method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A numerical model is developed for calculating the two-dimensional, unsteady, incompressible and turbulent flow within the rotating impeller and stationary volute of an industrial centrifugal pump. The objective is the investigation and comprehension of the instantaneous behaviour of centrifugal pumps, aiming at the reduction of vibrations, radial forces and hydraulic noise. The computation is performed within a blade-to-blade streamtube for the impeller and a tube normal to the axis of rotation for the volute. The equations to be solved are the unsteady Reynolds-averaged Navier-Stokes equations along with the continuity equation and the unsteady κ-ε equations for turbulence modelling. The finite volume method is applied for space discretization and an implicit scheme for time discretization. A multidomain overlapping grid technique is used for matching together the relative flow field calculated within the rotating impeller and the absolute one calculated within the stationary volute. In this way the impeller and volute interaction is directly taken into account. The numerical model is validated for a centrifugal pump of N q=32 under design flow conditions. Comparisons between calculation and measurements show fairly good agreement.
    Zusätzliches Material: 18 Ill.
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  • 164
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 449-465 
    ISSN: 0271-2091
    Schlagwort(e): aeroacoustic ; vortex shedding ; solid rocket motor ; implicit or explicit method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The present work is devoted to the numerical simulation of two important phenomena in the field of solid propellant rocket motors: the first is acoustic boundary layers that develop above the burning propellant; the other is a periodic vortex-shedding phenomenon which is the result of a strong coupling between the instability of mean flow shear layers and acoustic motions in the chamber. To predict the acoustic boundary layer, computations were performed for the lower half of a rectangular chamber with bottom-side injection. The outflow pressure is sinusoidally perturbed at a given frequency. For the highest CFL numbers the implicit scheme is not able to compute the unsteadiness in the acoustic boundary layer. With very low CFL numbers or with the explicit scheme the main features of the acoustic field are captured. To simulate the vortex-shedding mechanismin a segmented solid rocket motor, the explicit version is used. This computation shows a mechanism for ‘self-excited’ vortex shedding close to the second axial mode frequency. The use of the flux-splitting technique reduces substantially the amplitude of the oscillations. A few iterations are done with flux splitting, then the computation is performed without this technique. In this case both the frequency and the intensity are well predicted. A geometry more representative of the solid rocket motor is also computed. In this case the vortex-shedding process is more complex and pairing is observed.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 165
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 495-513 
    ISSN: 0271-2091
    Schlagwort(e): hydrodynamic planing ; vortex lattice ; jet modelling ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A three-dimensional numerical model using vortex lattice methods (VLMs) is developed to solve the steady planning problem. Planing hydrodynamics have similarities to the aerodynamic swept wing problem - the fundamental difference being the existence of a free surface. Details of the solution scheme are discussed, including the special features of the VLM used here in obtaining accurate flows at the leading and side edges. Computational results are presented and compared with existing theories and experiments.
    Zusätzliches Material: 17 Ill.
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  • 166
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 567-568 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 167
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 581-601 
    ISSN: 0271-2091
    Schlagwort(e): unstructured grids ; incompressible viscous flow ; pressure-correction method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: An unstructured grid, finite volume method is presented for the solution of two-dimensional viscous, incompressible flow. The method is based on the pressure-correction concept implemented on a semi-staggered grid. The computational procedure can handle cells of arbitrary shape, although solutions presented herein have been obtained only with meshes of triangular and quadrilateral cells. The discretization of the momentum equations is effected on dual cells surrounding the vertices of primary cells, while the pressure-correction equation applies to the primary-cell centroids and represents the conservation of mass across the primary cells. A special interpolation scheme s used to suppress pressure and velocity oscillations in cases where the semi-staggered arrangement does not ensure a sufficiently strong coupling between pressure and velocity to avoid such oscillations. Computational results presented for several viscous flows are shown to be in good agreement with analytical and experimental data reported in the open literature.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 168
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 915-917 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 169
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 431-444 
    ISSN: 0271-2091
    Schlagwort(e): laminar flows ; incompressible flows ; vorticity-streamfunction formulation ; Krylov subspace methods ; preconditioning ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A vorticity-streamfunction formulation for incompressible planar viscous flows is presented. The standard kinematic field equations are discretized using centred finite difference schemes and solved in a coupled way via a Newton-like linearization scheme. The linearized system of partial differential equations is handled through the restarting linear GMRES algorithm, preconditioned by means of an incomplete LU approximate factorization. The proposed solution technique constitutes a fast and robust algorithm for treating laminar flows at high Reynolds numbers. The pressure field is obtained at a subsequent step by solving a convection- diffusion equation in terms of the stagnation pressure, which presents certain advantages compared with the widely used static pressure Poisson equation. Results are shown for a wide variety of applications including internal and external flows.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 170
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996) 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 171
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 883-895 
    ISSN: 0271-2091
    Schlagwort(e): N-S solver ; Turbomachinery ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The internal flows inside a backswept centrifugal impeller at off-design point conditions are analysed by solving the fully three- dimensional Navier-Stokes equations coupled with the k-∊ two-equation turbulence model. Conditions analysed have flow rates of 85 per cent and 113 per cent of the design rate. The calculated results are compared with published experimental data and the comparison shows good agreement. A jet wake structure occurs near the outlet of the impeller for each of the two off-design flow rates and the location and size of the jet wake structure seem to be independent of the flow rate.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 172
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996) 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 173
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 987-989 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 174
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 163-176 
    ISSN: 0271-2091
    Schlagwort(e): convective heat transfer ; finite element method ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The purpose of this investigation is to study the convective heat transfer from a horizontal circular cylinder under the effect of a solid plane wall. The full Navier-Stokes and energy equations for two-dimensi onal steady flow are solved by a finite element method. The variations in surface shear stress, local pressure and Nusselt number around the surface of the cylinder as well as the predicted values of average Nusselt number, location of separation and some flow and temperature fields are presented. It is found that the average Nusselt number and drag force increase as the gap between the cylinder and the wall is increased.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 175
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 193-220 
    ISSN: 0271-2091
    Schlagwort(e): transition ; turbulence ; intermittency ; conditioning ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A differential method is proposed to simulate bypass transition. The intermittency in the transition zone is taken into account by conditioned averages. These are averages taken during the fraction of time the flow is turbulent or laminar respectively. Starting from the Navier-Stokes equations, conditioned continuity, momentum and energy equations are derived for the laminar and turbulent parts of the intermittent flow. The turbulence is described by a classical k-ε model. The supplementary parameter, the intermittency factor, is determined by a transport equation applicable for zero, favourable and adverse pressure gradients. Results for these pressure gradients are given.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 176
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 271-293 
    ISSN: 0271-2091
    Schlagwort(e): finite volume ; cell vertex ; pressure-velocity coupling ; high-resolution schemes ; non-orthogonal ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The steady, incompressible Navier-Stokes (N-S) equations are discretized using a cell vertex, finite volume method. Quadrilateral and hexahedral meshes are used to represent two- and three-dimensional geometries respectively. The dependent variables include the Cartesian components of velocity and pressure. Advective fluxes are calculated using bounded, high-resolution schemes with a deferred correction procedure to maintain a compact stencil. This treatment insures bounded, non-oscillatory solutions while maintaining low numerical diffusion. The mass and momentum equations are solved with the projection method on a non-staggered grid. The coupling of the pressure and velocity fields is achieved using the Rhie and Chow interpolation scheme modified to provide solutions independent of time steps or relaxation factors. An algebraic multigrid solver is used for the solution of the implicit, linearized equations.A number of test cases are anlaysed and presented. The standard benchmark cases include a lid-driven cavity, flow through a gradual expansion and laminar flow in a three-dimensional curved duct. Predictions are compared with data, results of other workers and with predictions from a structured, cell-centred, control volume algorithm whenever applicable. Sensitivity of results to the advection differencing scheme is investigated by applying a number of higher-order flux limiters: the MINMOD, MUSCL, OSHER, CLAM and SMART schemes. As expected, studies indicate that higher-order schemes largely mitigate the diffusion effects of first-order schemes but also shown no clear preference among the higher-order schemes themselves with respect to accuracy. The effect of the deferred correction procedure on global convergence is discussed.
    Zusätzliches Material: 14 Ill.
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  • 177
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 325-346 
    ISSN: 0271-2091
    Schlagwort(e): Taylor-Görtler-like vortices ; spiralling corner vortices ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: With the purpose of providing physical insight into the developing spanwise flow motion and identifying the presence of Taylor-Görtler- like vortices, we conducted a flow simulation in a rectangular cavity defined by a square cross-section and a spanwise aspect ratio of 3:1. The governing equations were solved for the transient processes by using a finite volume method in conjunction with segregated solution procedures. In the present work, attention is placed on the spiralling corner vortices near the two end walls and the longitudinal meandering Taylor-Görtler-like vortices. The investigated Reynolds number is taken to be 1500. As a vehicle for the present flow simulation, validation against analytic data was carried out first for a configuration similar to the problem of interest. This study demonstrates the feasibility of the employed computer code.
    Zusätzliches Material: 12 Ill.
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  • 178
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 413-414 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 179
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 467-483 
    ISSN: 0271-2091
    Schlagwort(e): general BEM ; non-linear operators ; homotopy ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In this paper the well-known non-linear equation f‴+½ff″=0 with boundary conditions f(0)=0, f′(0)=0 and f (∞)=1 is used as an example to describe the basic ideas of a kind of general boundary element method for non-linear problems whose governing equations and boundary conditions may not contain any linear terms at all.
    Zusätzliches Material: 10 Ill.
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  • 180
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 897-921 
    ISSN: 0271-2091
    Schlagwort(e): Navier-Stokes equations ; unsteady flow ; laminar flow ; turbulent flow ; projection method ; approximate factorization technique ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In this paper an implicit projection method for the solution of the two-dimensional, time-dependent, incompressible Navier- Stokes equations is presented. The basic principle of this method is that the evaluation of the time evolution is split into intermediate steps. The computational method is based on the approximate factorization technique. The coupled approach is used to link the equations of motion and the turbulence model equations. The standard k-∊ turbulence model is used. The current methodology, which has been tested extensively for steady problems, is now applied for the numerical simulation of unsteady flows. Several cases were tested, such as plane or axisymmetric channels, a backward-facing step, a square cavity and an axisymmetric stenosis.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 181
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 567-588 
    ISSN: 0271-2091
    Schlagwort(e): multiblock ; turbulent flow ; computational modelling ; parallel computing ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A multiblock algorithm for general 2D and 3D turbulent flows is introduced and applied to three cases: a compressor cascade passage, a two-element high-lift aerofoil and a round-to-square transition duct. The method is a generalization of a single-block scheme which is based on a non-orthogonal, fully collocated finite volume framework, applicable to incompressible and compressible flows and incorporating a range of turbulence transport models, including second-moment closure. The multiblock implementation is essentially block-unstructured, each block having its own local co-ordinate system unrelated to those of its neighbours. Any one block may interface with more than one neighbour along any one block face. Interblock communication is handled by connectivity matrices and effected via a two-cell overlap region along block boundaries in which ‘halo data’ reside. The algorithm and the associated data communication are explained in detail, and its effectiveness is verified, with particular reference to improved numerical resolution and parallel computing.
    Zusätzliches Material: 22 Ill.
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  • 182
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 635-635 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 183
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 673-690 
    ISSN: 0271-2091
    Schlagwort(e): Euler equations ; directionally adaptive meshes ; edge-based error estimate ; structured grids ; mesh movement ; finite element method ; high-speed flows ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The present paper describes a directionally adaptive finite element method for high-speed flows, using an edge-based error estimate on quadrilateral grids. The error of the numerical solution is estimated through its second derivatives and the resulting Hessian tensor is used to define a Riemannian metric. An improved mesh movement strategy, based on a spring analogy, but with no orthogonality constraints, is introduced to equidistribute the lengths of the edges of the elements in the defined metric. The grid adaptation procedure is validated on an analytical test case and the efficiency of the overall methodology is investigated on supersonic and hypersonic benchmarks.
    Zusätzliches Material: 21 Ill.
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  • 184
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 691-710 
    ISSN: 0271-2091
    Schlagwort(e): viscoelastic ; extensional flow ; wirecoating ; Taylor-Galerkin ; finite elements ; pressure-correction ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The numerical simulation of three model viscoelastic extensional flows is considered: sink flow, model draw-down and conical section draw-down. A transient finite element scheme with a pressure correction method is employed to analyse the numerical treatment of such problems for Oldroyd- Band Phan-Thien/Tanner constitutive models. Both decoupled and coupled formulations are compared for these highly convective flows and effective mechanisms are proposed for removing numerical oscillations in the temporally developing solution. In pure viscoelastic extensional flow from an initial stress-free state, the maximum stress level attained decreases with increase in material relaxation time. When this is followed by stress relaxation, as in conical section draw-down, increasing the relaxation time inhibits stress decay.
    Zusätzliches Material: 14 Ill.
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  • 185
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 811-817 
    ISSN: 0271-2091
    Schlagwort(e): SIMPLE-like algorithms ; average correction technique ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: This note develops an average correction technique for accelerating the rate of convergence of the SIMPLE-like algorithm by implementing the average pressure correction method as proposed by Wen and Ingham (Int. j. numer. methods fluids, 17, 385-400 (1993); 19, 889-903 (1994)) with an average velocity correction. The technique is illustrated by considering the classical problem of fluid flow over a backward-facing step using (i) no average correction, (ii) an average velocity correction, (iii) an average pressure correction and (iv) both average velocity and pressure corrections. When both average velocity and pressure corrections are employed, it is found that the number of iterations required for convergence is almost independent of the initial guessed values of fluid velocity and pressure and the fastest rate of convergence may be achieved.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 186
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 753-785 
    ISSN: 0271-2091
    Schlagwort(e): numerical simulation ; spectral time discretization ; Navier-Stokes equations ; laminar flow ; shear flow ; unsteady flow ; periodic flow ; instability ; Hopf bifurcation ; non-linearity ; non-linear theory ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The onset of the Bénard-von Kármán instability consisting of the selective amplification of the linear unstable mode and yielding finally the well-known saturated state has been described many times on the basis of both numerical and experimental results in various configurations. However, neither the role of the harmonics and their coupling has been examined quantitatively, nor has the spatial structure of the instability been studied in detail. A recently developed numerical method of simulation of quasi-periodic flows makes it possible to integrate the investigation of linear and non-linear characteristics within a single numerical method. The simulation of the 2D afterbody wake presented in this paper allows us to follow the amplification of the instability over many orders of magnitude. It is shown that at all stages of its development the instability is characterized by a series of harmonics, each of them amplified with a multiple of the fundamental amplification rate during the linear regime. The amplification of harmonics results from an energy transfer from the mean flow to harmonics of increasingly higher order. Ultimately the energy losses compensate this transfer and an equilibrium, commonly called saturation of the instability, is reached. It is shown that the coupling between the fundamental harmonic and the mean flow is mainly responsible for the saturation. The convergence rate of the development of the instability into harmonics is investigated. A full description of the spatial structure of all significant harmonics both in the linear regime and at saturation is obtained. The results show that time and space characteristics of the instability can be investigated simultaneously in an efficient way. Such an approach might be particularly important in 3D wakes where the geometry has a strong influence on the behaviour of unstable flows.
    Zusätzliches Material: 27 Ill.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 923-936 
    ISSN: 0271-2091
    Schlagwort(e): advection-diffusion ; multidimensional upwinding ; finite elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Multidimensional residual distribution schemes for the convection-diffusion equation are described. Compact upwind cell vertex schemes are used for the discretization of the convective term. For the diffusive term, two approaches are compared: the classical finite element Galerkin formulation, which preserves the compactness of the stencil used for the convective part, and various residual-based approaches in which the diffusive term, evaluated after a reconstruction step, is upwinded along with the convective term.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 188
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 29-41 
    ISSN: 0271-2091
    Schlagwort(e): wake ; curvature ; pressure gradient ; k-ε model of turbulence ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Experimental data on the development of wakes in a straight duct, a curved duct, a curved diffuser and a straight diffuser are compared with computations based on a finite volume scheme incorporating the k- ε model of turbulence. The results show that the computations based on the standard k-ε model are able to satisfactorily capture only the mean velocity profiles. To improve the predictions, several modifications to the model are tried out. Close agreement between experiment and computation as regards the velocity profiles, wake parameters and profiles of the turbulent kinetic energy k and Reynolds shear stress ⊼{uv} is obtained when modification to the model constant Cμ, based on the curvature parameter and the ratio of the production of turbulent kinetic energy to its rate of dissipation, is incorporated. The modified model is also able to capture the asymmetry in the profiles of k and ⊼{uv} caused by the curvature and its enhancement due to the additional presence of an adverse pressure gradient.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 189
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 103-120 
    ISSN: 0271-2091
    Schlagwort(e): free surface ; free boundary problem ; segregated method ; finite elements ; extrusion ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: An algorithm to simulate steady, viscous free surface flows is presented in this paper. A Picard-type approach wherein the flow and free surface updates are performed alternately is utilized to iterate for a solution. The procedure is intended for large-scale two- or three-dimensional problems. A surface-intrinsic co-ordinate system which facilities representation of general free surface shapes is used. Using a Galerkin finite element method (GFEM), two free surface updates, namely kinematic and normal stress updates are formulated. It is shown that the effects of surface tension, surface tension gradients and imposition of contact angles can be simulated elegantly within the framework of the GFEM. A novel feature of the updates is that the deformations are sought in a direction normal to the current iterate free surface shape, with the result that the method is ideally suited when used in conjunction with an automatic mesh generator. With the normal stress update a volume constraint can also be imposed. A segregated method is utilized to solve iteratively one degree of freedom at a time for the solution of the flow variables. As a result, the memory and disc space requirements are minimal. Sample problems in extrusion, coating and crystal growth are presented to clearly illustrate the convergence behaviour and accuracy of the algorithm.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 190
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 121-135 
    ISSN: 0271-2091
    Schlagwort(e): spatial marching methods ; reduced Navier-Stokes equations ; explicit methods ; Runge-Kutta method ; hypersonic flow ; supersonic flow ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: This paper develops a spatial marching method for high-speed flows based on a finite volume approach. The method employs the reduced Navier- Stokes equations and a pressure splitting in the streamwise direction based on the Vigneron strategy. For marching from an upstream station to one downstream the modified five-level Runge-Kutta integration scheme due to Jameson and Schmidt is used. In addition, for shock handling and for good convergence properties the method employs a matrix form of the artificial dissipation terms, which has been shown to improve the accuracy of predictions. To achieve a fast rate of convergence, a local time-stepping concept is used. The method retains the time derivative in the governing equations and the solution at every spatial station is obtained in an iterative manner.The developed method is validated against two test cases: (a) supersonic flow past a flat plate; and (b) hypersonic flow past a compression corner involving a strong viscous-inviscid interaction. The computed wall pressure and wall heat transfer coefficients exhibit good general agreement with previous computations by other investigators and with experiments.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 191
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 223-224 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 192
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 265-281 
    ISSN: 0271-2091
    Schlagwort(e): unstructured ; SIMPLE ; finite volume ; cell-centred ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A pressure correction procedure for general unstructured meshes is presented. It is a cell-centred, collocated finite volume method and the pressure-velocity coupling is treated using SIMPLEC. The cells can have an arbitrary number of grid points (cell vertices). In the present study the number of faces on the cells varies between three and six. The discretized equations are solved using either a symmetric Gauss-Seidel solver or a conjugate gradient solver with a preconditioner. The method is applied to three two-dimensional test cases in which the flow is incompressible and laminar. The extension to three dimensions as well as to turbulent flow using transport models is straightforward. It can also be extended to handle compressible flow.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 193
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 323-324 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 194
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 375-392 
    ISSN: 0271-2091
    Schlagwort(e): gates ; finite elements ; potential flow ; free surface ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Two-dimensional finite element analyses of two types of gate - (i) a conduit gate with pressure flow upstream of the gate and free surface flow downstream of the gate and (ii) a sluice gate with free surfaces both upstream and downstream of the gate - are done using ideal fluid theory. The conduit gate problem is solved using both Φ- and Ψ- formulations. Various methods of satisfying the boundary conditions were tested for both formulations. The ψ-formulation developed in the present study is found to converge faster for flows with Froude numbers less than 4, which are common in sluice gates. The results obtained from the present study are compared with results from analytical and experimental techniques available in the literature. The ψ-formulation developed in the present study is then used to solve the spillway gate problem, for which no analytical solution is available.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 195
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 429-444 
    ISSN: 0271-2091
    Schlagwort(e): modified Boussinesq equations ; finite element method ; wave-current interaction ; breaking waves ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A two-dimensional (horizontal plane) coastal and estuarine region model, capable of predicting the combined effects of gravity surface shallow- water waves (shoaling, refraction, diffraction, reflection and breaking), and steady currents, is described and numerical results are compared with those obtained experimentally.Two series of observations within a wave flume and a combined wave-current facility were developed. In the first case, the wave was generated via a hinged paddle located within a deepened section at one end of the channel, as, in the second case, the wave propagating with or against the current was generated by a plunger-type wavemaker; the re-circulating current was introduced via one passing tank connected to a centrifugal pump.Several comparisons for a number of 1D situations and one 2D horizontal plane case are presented.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 196
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 483-493 
    ISSN: 0271-2091
    Schlagwort(e): Navier-Stokes equations ; Oseen equations ; method of lines ; artificial boundary condition ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: We design an artificial boundary condition for the steady incompressible Navier-Stokes equations in streamfunction-vorticity formulation in a flat channel with slip boundary conditions on the wall. The new boundary condition is derived from the Oseen equations and the method of lines. A numerical experiment for the non-linear Navier-Stokes equations is presented. The artificial boundary condition is compared with Dirichlet and Neumann boundary conditions for the flow past a rectangular cylinder in a flat channel. The numerical results show that our boundary condition is more accurate.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 197
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996) 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 198
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 569-580 
    ISSN: 0271-2091
    Schlagwort(e): magnetohydrodynamics ; Godunov ; upwind ; conservative ; plasma ; fusion ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: In this paper a higher-order Godunov method for one-dimensional solutions of the ideal MHD (magneto-hydrodynamics) equations is presented. The method uses a fluctuation approach and includes a new sonic fix and a new Roe averaging. After a short introduction the MHD equations in conservative form are given. The flux is rearranged such that the eigenstructure is not changed. This rearrangement allows full Roe averaging for any value of adiabatic index (contrary to Brio and Wu's conclusion). A new procedure to get Roe - averaged MHD fields at the interfaces between left and right states is then presented and some useful identities are given. Next the second-order-limited fluctuation approach is presented in full detail. The new sonic fix for MHD and the procedure for applying this fix to the sonic points are then given in detail. Numerical results obtained with the described method are presented. Finally, conclusions are given.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 199
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 643-671 
    ISSN: 0271-2091
    Schlagwort(e): spectral and finite elements ; polynomial-exponential elements ; boundary layers ; connection-diffusion ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The purpose of this paper is to present a new algorithm for the resolution of both interior and boundary layers present in the convection-diffusion equation in laminar regimes, based on the formulation of a family of polynomial- exponential elements. We have carried out an adaptation of the standard variational methods (finite element method and spectral element method), obtaining an algorithm which supplies non-oscillatory and accurate solutions. The algorithm consists of generating a coupled grid of polynomial standard elements and polynomial-exponential elements. The latter are able to represent the high gradients of the solution, while the standard elements represent the solution in the areas of smooth variation.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 200
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 689-690 
    ISSN: 0271-2091
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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