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Numerical simulation of delayed die swell (1990)

Delvaux, V. ; Crochet, M. J.

Springer

Rheologica acta 29 (1990), S. 1-10

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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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Transient finite element method for calculating steady state three-dimensional free surfaces (1992)

Wambersie, O. ; Crochet, M. J.

Chichester : Wiley-Blackwell

International Journal for Numerical Methods in Fluids 14 (1992), S. 343-360

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ISSN: 0271-2091

Keywords: Free surfaces ; Extrusion ; Conjugate gradients ; Finite elements ; Three-dimensional free surfaces ; Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: In order to reduce the cost of large three-dimensional calculations of steady state free surfaces, we have combined a time-dependent approach, a decoupling algorithm and a conjugate gradient solver along the lines introduced earlier by Gresho and Chan. The free surface is calculated separately by applying the kinematic condition to a number of faces defined on the undeformed surface. For the pseudo-time-marching technique we show that it is economical to adopt different time steps for the free surface calculation and the other fields. The accuracy of the method is tested on the well-known circular die problem; the method is then used to reveal the effects of inertia and shear thinning on square and rectangular dies.

Additional Material: 15 Ill.