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  • 1
    Electronic Resource
    Electronic Resource
    Non-linear viscoelastic behavior of fumed silica suspensions (1999)
    Springer
    Rheologica acta 38 (1999), S. 14-25 
    Details
    ISSN: 1435-1528
    Keywords: Key words Fumed silica ; Colloidal suspensions ; Non-linear viscoelasticity ; Rheological models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Suspensions of fumed silica exhibit a wide range of rheological properties depending on the nature and magnitude of the interparticle forces. In a non-polar fluid, the particles interact through hydrogen bonding and can form a three-dimensional network. The microstructure formation is responsible for the non-linear viscoelastic behavior of fumed silica suspensions, even at very small strain. These non-linear rheological properties have been studied in small amplitude oscillatory experiments as a function of particle size, surface treatment of particles, suspending medium polarity and solids concentration. The non-linear viscoelastic behavior is characterized by a non-sinusoidal waveform of the signal response. For suspensions in a non-polar fluid, both the elastic and the loss moduli are shown to be sensitive to the strain amplitude: the elastic modulus is decreasing with increasing strain whereas the loss moduli is initially increasing with strain. We have chosen to examine the dissipated energy which is clearly related to the breakup of the suspension structure. A comparison of model predictions and the experimental data shows the limitations of these models, recently proposed in the literature to describe the behavior of colloidal suspensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003970050152
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  • 2
    Electronic Resource
    Electronic Resource
    A numerical comparison of two decoupled methods for the simulation of viscoelastic fluid flows (1990)
    Springer
    Rheologica acta 29 (1990), S. 342-351 
    Details
    ISSN: 1435-1528
    Keywords: Oldroyd-B fluids ; die flows ; stick-slip problem ; finite element method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Two decoupled methods for the finite element solution of the planar stick-slip transition problem with Oldroyd-B fluids, namely the method of characteristics and the Lesaint-Raviart technique, are presented and compared. These procedures are used for the local treatment of the stress transport equation imbedded in the constitutive law and allow the approximation of stresses with discontinuous shape functions. Computations are carried out up to a Deborah number of 4 and the methods are shown to yield fairly similar results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01339889
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  • 3
    Electronic Resource
    Electronic Resource
    An adaptive domain decomposition method for simulation of transport in porous media (1988)
    Springer
    Transport in porous media 3 (1988), S. 549-562 
    Details
    ISSN: 1573-1634
    Keywords: Adaptive mesh ; finite element method ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A Galerkin finite element method is used along with a self-adaptive strategy of domain discretisation to model dispersion in an axisymmetric cylindrical porous medium. A solution strategy is proposed based on the use of a Gear scheme for the time stepping and partial vectorisation of the code. The domain is highly discretised in the area of the sharp transient front, while the remainder is coarsely discretised. The area covered by the fine mesh is determined by the value of the local concentration gradients. Numerical results are presented for the one and two dimensional cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959102
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  • 4
    Electronic Resource
    Electronic Resource
    A study of two-dimensional dispersion in unconsolidated porous media (1990)
    Springer
    Transport in porous media 5 (1990), S. 269-286 
    Details
    ISSN: 1573-1634
    Keywords: Dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An experimental and numerical investigation into the magnitude of longitudinal and transverse dispersion in a two-dimensional flow field over a particle Peclet number range of 50–8500 is reported. Numerical modelling using a Galerkin finite element method is used to test various models, notably those of Fried and combarnous and Koch and Brady. Dispersion at low Peclet numbers (〈 200) is found to be described adequately by either model, which at large Peclet, the degree of dispersion is significantly underestimated. An improved dispersion model for Peclet numbers greater than 200 is proposed. The transverse dispersion term and the choice of inlet boundary condition are found to have a negligible effect on the shape of the breakthrough curve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00140016
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  • 5
    Electronic Resource
    Electronic Resource
    Modelling of Fluid/Paper Interaction in the Application Nip of a Film Coater (2000)
    Springer
    Transport in porous media 40 (2000), S. 55-72 
    Details
    ISSN: 1573-1634
    Keywords: paper coating ; simulation ; free surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper describes a model for the penetration of fluid into a moving paper web in the application nip of a film coater. One-dimensional and two-dimensional solution methods are developed and compared. The two-dimensional model is solved using a Galerkin finite element method with a free surface algorithm. The depth of fluid penetration into the paper web increases with increase in applied pressure, paper permeability and exposure time. The fluid penetration depth decreases as the porosity or solution viscosity increases. The functional relationship among these variables depends on the profile of the pressure applied at the surface of the paper sheet. For the case of uniform paper permeability and no air compression in the web, the two-dimensional model gives similar results to the one-dimensional model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006680607586
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  • 6
    Electronic Resource
    Electronic Resource
    Finite element analysis of viscous mixing with a helical ribbon-screw impeller (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 939-944 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A finite element analysis was carried out to study the mixing patterns of a viscous Newtonian fluid into a stirred tank. A helical ribbon screw impeller (HRS) was used as the mixing device. The numerical simulation involved the full three-dimensional resolution of the equations of change governing the flow in the tank. The circulation time and the torque were determined and compared with experimental data. A good agreement was found, showing the usefulness of the numerical approach for design purposes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380614
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  • 7
    Electronic Resource
    Electronic Resource
    Parallel finite element computations on a network using NCS (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 251-258 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Research has been carried out on the use of NCS (Network Computing System) to distribute the processing of a finite element application to multiple computers at once. Coarse-grained parallelism of specific routines on loosely coupled CPUs has been implemented and tested. In a step-by-step fashion, the method of using NCS to convert finite element software POLY2D is explained for its application in parallel computing resources throughout a network. For the modeling of a simple conductive heat transfer problem, the distributed version of POLY2D on a homogeneous token ring network of nine Apollo workstations is used. Some timings given are compared to those obtained from a standard nondistributed simulation.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380211
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  • 8
    Electronic Resource
    Electronic Resource
    Non-Isothermal mixing of rheologically complex fluids with close-clearance impellers: Effect of natural convection (1997)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 203-207 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient heat transfer in a mechanically agitated vessel is studied in the case of an anchor and an helical ribbon impeller using Newtonian and shear thinning fluids. Temperature stratification is found more pronounced with the anchor, making this impeller clearly inadequate for heat transfer. The impact of natural convection is evaluated first using the classical Gr/Re2 ratio. It is shown that the use of this criterion in viscous mixing is somewhat misleading. A new Grashof number is then proposed to assess the significance of the viscous and buoyancy effects in non-isothermal, non-Newtonian mixing applications. It is shown that the interpretation of this new number is strongly related to the concept of process viscosity.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270200308
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  • 9
    Electronic Resource
    Electronic Resource
    A decomposed Crouzeix-Raviart element for the finite element solution of the Navier-Stokes equation (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 13 (1991), S. 1073-1083 
    Details
    ISSN: 0271-2091
    Keywords: Crouzeix-Raviart ; Analytical integration ; Brezzi-Babuška condition ; Navier-Stokes ; Finite element method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A methodology for the decomposition of the Crouzeix-Raviart finite element into six linear subelements is described. The resulting element is shown to satisfy the Brezzi-Babuška compatibility condition. The error bounds are also established. A comparison in accuracy between this and the standard Crouzeix-Raviart element is presented for driven cavity flows. Other results include the execution time for the DCR element and the Crouzeix-Raviart element along with both analytical and numerical integration. It is shown that the decomposed element results in shorter execution times with only marginal changes in accuracy.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650130902
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  • 10
    Electronic Resource
    Electronic Resource
    Three-dimensional adaptive finite element computations and applications to non-Newtonian fluids (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 13 (1991), S. 145-165 
    Details
    ISSN: 0271-2091
    Keywords: Finite elements ; Meshing ; Adaptivity ; Navier-Stokes ; Power law ; Error estimation ; 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: An adaptive strategy for the finite element solution of three-dimensional viscous flow problems is defined and implemented. The solution strategy is based on an advancing front mesh generator making use of binary data structures for fast geometrical data handling. The error is estimated a posteriori with a residual-type bound. The error estimate is shown to exhibit proper convergence for tetrahedral elements. Its combination with the mesh generator and an interpolation scheme for unstructured meshes is shown to generate adaptive meshes and to reduce the solution cost for a given error level, as illustrated by the isothermal flow of a shear-thinning fluid.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650130203
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