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  • 1
    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
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An unstructured mesh generator is integrated in a finite element solver for the adaptive solution of non-Newtonian fluid flows. An a posteriori error estimate for the equations of motion is presented and is shown to behave according to theoretical convergence rates. The estimate is used to drive the refinement process, and the resulting iterative remeshing algorithm leads to reduction of the error level in the case of an axisymmetric contraction. Original data structures used to speed-up remeshing and interpolation between unstructured grids are also presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Several old and new tetrahedral elements are tested and compared to some classical hexahedral elements for the solution of three-dimensional incompressible fluid flow problems. The proposed elements are created by adding velocity degrees of freedom to the basic trilinear velocity, constant pressure tetrahedron so as to satisfy the Brezzi condition. Numerical tests carried out for an artificial divergence-free flow problem and the lid-driven cubic cavity up to a Reynolds number of 400 are used to compare the proposed elements and assess their accuracy.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 529-533 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermal dependence of the parameters of the Carreau A model of viscosity has been investigated for 13 polymeric resins. It was shown that the zero-shear viscosity and the time constant obey an Arrhenius-type law and that, for these parameters, compensation effects are exhibited. The shear-thinning index was found to be fairly independent of temperature. An important consequence of a compensation effect is that only one determination of a parameter at a given temperature gives the complete temperature-dependence of this parameter.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 971-979 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Lubrication theory has been applied to solve flow problems in profile extrusion dies without flow separations, for Newtonian and power law type fluids. The method is based on velocity calculation within cross sections perpendicular to the flow. Pressure drop can also be obtained from a macroscopic balance, if the flow rate is known. Comparison of pressure drops in 2-D and 3-D geometries has been made with numerical simulation obtained by a finite element method. Results show a good accuracy of the proposed method.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new graphical representation for fluid flow is explained. It combines the concepts of classical streamline plot and velocity vector display and enables a more adequate visualization of flow pattern, especially near solid boundaries.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computer model is proposed to simulate the flow of molten polymer in the melt conveying zone of extruders provided with mixing pins. This model is based on the calculation of down-channel velocities within cross sections perpendicular to the flow. A Lagrangian reference frame (i.e. that of the barrel sliding on top of the channel) is used to describe the flow in a convenient manner, the mixing pins being represented as a set of virtual boundary conditions (geometric constraints). The proposed method is compared to a full 3D finite element flow simulation with Newtonian and non-Newtonian fluids showing a good agreement in term of the pressure drop calculation. Numerical tests are also carried out in the case of a rigid PVC compound used for window profile extrusion. The adequacy found between the predictions and experimental measurements obtained on an industrial extruder confirms the performance of the proposed model.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 10
    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
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