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  • 1
    Electronic Resource
    Electronic Resource
    Newtonian stratified flow through an abrupt expansion (1987)
    Springer
    Rheologica acta 26 (1987), S. 401-413 
    Details
    ISSN: 1435-1528
    Keywords: Numerical simulation ; coextrusion ; abruptexpansion ; Newtonianflow ; stratifiedflow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The present paper is devoted to the numerical simulations of stratified generalized Newtonian flow. The main feature of the algorithm is to include the coordinates of the interface as primitive unknowns of the flow problem together with the nodal velocity components and pressures calculated on a deformable finite element mesh. Newton-Raphson's iterative method is used for solving the non-linear problem. Special attention is given to the location of the intersection between the interface and a solid boundary, when it is unknown at the outset. The method is applied to the creeping stratified flow of two Newtonian fluids through a one-to-four abrupt expansion; the results remain valid for the contraction problem. It is found that, under appropriate conditions, the small Newtonian corner vortex can increase by a large factor, both in size and intensity; the degrees of freedom of the simulation are the ratios of flow-rate and of viscosity of the fluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01333840
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  • 2
    Electronic Resource
    Electronic Resource
    Finite elements for viscoelastic flows with change of type (1993)
    Springer
    Theoretical and computational fluid dynamics 4 (1993), S. 289-308 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We compare several mixed finite-element methods for calculating viscoelastic flows where the vorticity equation changes type from elliptic to hyperbolic whenever inertia is taken into account. The flows are perturbed viscometric flows with slightly wavy walls. The perturbed uniform flow gives rise to a closed-form analytical solution. We examine five different finite-element algorithms; it is found that the so-called SU4×4 and EVSS methods perform much better than the other three. We also examine a number of features proper to flows with change of type, such as the propagation of disturbances along characteristic lines of the vorticity equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418778
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  • 3
    Electronic Resource
    Electronic Resource
    Time-dependent numerical simulation of viscoelastic flow and stability (1993)
    Springer
    Theoretical and computational fluid dynamics 5 (1993), S. 57-75 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The 4×4 mixed finite-element method is extended in order to calculate time-dependent viscoelastic flow. The basic algorithm uses a fully implicit technique with a predictor-corrector control of the time step for monitoring the accuracy. Excellent agreement is found with analytical test cases. Several decoupled schemes are also developed with a view to reducing the cost of the time-dependent calculations. However, none of them reaches that goal on actual flow problems because of a drastic reduction of the time step. The time-dependent algorithm is used for verifying the stability of steady-state viscoelastic flow solutions. The approach consists of using a steady-state solution as a set of initial conditions for a time-dependent algorithm with the hope that, in case of instability, the system will lead to a stable solution. More precisely, we consider the flow of an Oldroyd-B fluid through a four-to-one contraction. Starting from a steady-state flow, we impose a pressure impulse in the entry section and calculate the approach toward another steady-state. For planar contractions, we do not constrain the flow to be symmetric while, for circular contractions, the flow is endowed with swirling capabilities. It is found that the stable or unstable character of the flow depends upon the mesh as well as upon the method of discretization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311811
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  • 4
    Electronic Resource
    Electronic Resource
    A mixture of two simple materials (1971)
    Springer
    Acta mechanica 12 (1971), S. 189-208 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Auf der Grundlage der thermodynamischen Theorie vonGreen undNaghdi [1] werden die Materialgleichungen für ein Gemisch von zwei einfachen Stoffen hergeleitet. Besonders untersucht wird ein Gemisch von zwei einfachen Flüssigkeiten, dessen Bewegung in der jüngsten Vergangenheit langsam war.
    Notes: Summary Constitutive relations for a mixture of two simple materials with fading memory are derived, based on the thermodynamical theory proposed byGreen andNaghdi [1]. Special attention is devoted to a mixture of two simple fluids the motion of which has been slow in recent past.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277583
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  • 5
    Electronic Resource
    Electronic Resource
    Small motions superposed on large static deformations in porous media (1967)
    Springer
    Acta mechanica 4 (1967), S. 315-335 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die Feld- und Materialgleichungen für ein flüssigkeitsgefülltes, poröses elastisches Medium werden unter der Voraussetzung kleiner Bewegungen, die großen statischen Deformationen überlagert sind, hergeleitet. Hierbei wird die in [3] entwickelte Theorie benützt. Zwei Beispiele einer Parallelströmung in einem anfangs einer homogenen Deformation unterworfenen Medium werden diskutiert. Desgleichen wird für eine Klasse stationärer Strömungen eine Darstellung der Lösungen der infinitesimalen Theorie (analog derBoussinesq-Papkovich-Darstellung) hergeleitet.
    Notes: Summary This paper is concerned with the development of the field equations and constitutive equations for small motions superposed on large static deformation of a liquid-filled porous elastic solid, using the basic theory of interacting continua given in [3]. Two examples of parallel flow in a medium which initially is subjected to a homogeneous deformation are discussed. Also a representation for the solutions of the equations of the infinitesimal theory (analogous to theBoussinesq-Papkovich representation) is deduced for a class of steady flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01591575
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  • 6
    Electronic Resource
    Electronic Resource
    On the stability of plane poiseuille flow of viscoelastic fluids (1976)
    Springer
    Acta mechanica 24 (1976), S. 1-12 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Untersucht wird die Stabilität der ebenen Poiseuille-Strömung einer endlichen linear-viskoelastischen Flüssigkeit bei ebenen infinitesimalen Störungen. Die Gedächtnisfunktion wird auf der Grundlage des Kugel-Feder-Modells der Molekulartheorie verdünnter Polymerlösungen erhalten. Die Untersuchung zeigt den destabilisierenden Einfluß des viskoelastischen Charakters der Flüssigkeit; für kleine Weissenberg-Zahlen hat die Größe der Relaxationszeit geringen Einfluß auf die Stabilität. Ebenfalls untersucht wird der Einfluß eines zusätzlichen Newtonschen Gliedes in der Werkstoffbeziehung einer endlichen linear-viskoelastischen Flüssigkeit.
    Notes: Summary We consider the stability of plane Poiseuille flow under plane infinitesimal disturbances of a finite linear viscoelastic fluid. The memory function is obtained on the basis of the bead-spring model in the molecular theory of dilute polymer solutions. The analysis shows the destabilizing influence of the viscoelastic character of the fluid; for small Weissenberg numbers, the number of relaxation times has little influence upon stability. The effect upon stability of the addition of a newtonian term in the stress constitutive relation of a finite linear viscoelastic fluid is also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175753
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  • 7
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1968)
    Springer
    Acta mechanica 5 (1968), S. 208-212 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178833
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  • 8
    Electronic Resource
    Electronic Resource
    Numerical simulation of delayed die swell (1990)
    Springer
    Rheologica acta 29 (1990), S. 1-10 
    Details
    ISSN: 1435-1528
    Keywords: Delayed dieswell ; criticalextrusionvelocity ; Oldroyd-B ; viscoelasticMach number ; Giesekus fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract In a recent paper, Joseph et al. showed that, for a number of viscoelastic fluids, one can observe the phenomenon of delayed die swell beyond a critical extrusion velocity, or beyond a critical value of the viscoelastic Mach number. Giesekus had also observed that delayed die swell is a critical phenomenon. In the present paper, we find a set of material and flow parameters under which it is possible to simulate delayed die swell. For the viscoelastic flow calculation, we use the finite element algorithm with sub-elements for the stresses and streamline upwinding in the discretized constitutive equations. For the free surface, we use an implicit technique which allows us to implement Newton's method for solving the non-linear system of equations. The fluid is Oldroyd-B which, in the present problem, is a singular perturbation of the Maxwell fluid. The results show very little sensitivity to the size of the retardation time. We also show delayed die swell for a Giesekus fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01331795
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  • 9
    Electronic Resource
    Electronic Resource
    On thermal effects in a special class of viscoelastic fluids (1973)
    Springer
    Rheologica acta 12 (1973), S. 321-329 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Summary A brief account of a non-isothermal theory of a restricted class of viscoelastic fluids with fading memory followed by its application to some special viscometric flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01635123
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stresses during annealing of a glass ribbon (1973)
    Springer
    Rheologica acta 12 (1973), S. 330-336 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01635124
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    Paper (German National Licenses)
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