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Dec 1978

Volume 22, Issue 6, pp. 571-668


Velocity Field Rearrangement in Stagnation Flow Leading to Diverging Radial Flow Between Parallel Plates

Lawrence R. Schmidt

J. Rheol. 22, 571 (1978); http://dx.doi.org/10.1122/1.549490 (18 pages)

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Velocity field rearrangement in tube flow followed by stagnation flow and diverging radial flow between parallel plates has been investigated with a polypropylene melt and composites of solid glass beads in a polypropylene melt. The tube axis was aligned normal to the parallel plates, creating a stagnation flow at the inlet to the diverging flow channel. Pigmented tracer elements, placed at precise locations in the tube, illustrated flow patterns which were recorded on 16 mm movie film. After an analysis of the film, the diagonal components of the rate‐of‐deformation tensor were computed at several different positions in the flow channel. From the sign and relative magnitude of the diagonal components the basic types of extensional flow were identified. The flow behavior of the polypropylene and the bead‐filled polypropylene in the complex channels is essentially the same despite large differences in the rheological and physical properties of the composites. Although the tracer technique needs to be refined for stagnation flows, the reduced tracer data show that the inlet effects associated with the complex stagnation flow extend from the stagnation point a distance of 5–10 times the plate separation. The flow in this region is a combination of shear and complex extensional flows. Beyond this inlet region the flow is somewhat less complex and can be described as a combination of planar extension and simple shear.
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83.50.Jf Extensional flow and combined shear and extension
83.80.Rs Polymer solutions
83.80.Sg Polymer melts

RQP Method of Inferring a Mechanical Relaxation Spectrum

D. R. Wiff

J. Rheol. 22, 589 (1978); http://dx.doi.org/10.1122/1.549491 (9 pages)

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The Regularization‐Quadratic Programming (RQP) method is used to circumvent the inherent ill‐posedness of integral equations of the first kind found in the theory of linear viscoelasticity. The ability of this method to detect sharp “cutoffs” in a relaxation spectrum is investigated. Finally, the method is applied to standard master curve polyisobutylene data in order to substantiate the ability to reliably predict sharp boundaries and the overall spectrum shape. The results are very encouraging since no prior assumptions were made as to the functional shape of the sought‐after relaxation spectrum.
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83.85.Ns Data analysis (interconversion of data computation of relaxation and retardation spectra; time-temperature superposition, etc.)

Rheological Behavior of Flocculated and Dispersed Aqueous Kaolin Suspensions in Pipe Flow

N. I. Heywood and J. F. Richardson

J. Rheol. 22, 599 (1978); http://dx.doi.org/10.1122/1.549492 (15 pages)

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The flow behavior of both highly flocculated and dispersed kaolin suspensions has been studied using a capillary tube viscometer and two horizontal pipeline test loops. These facilities enabled wall shear rates to be varied from 30 to 11,000 sec−1. Experiments were carried out in which volumetric solids concentrations ranged from 8.6 to 23.4% for the flocculated suspensions, and from 23.4 to 38.7% for the dispersed suspensions. Over the shear rate range 30–1000 sec−1, the rheograms for laminar flow of the flocculated suspensions followed the Ostwald‐de Waele power law model, while for the higher shear rate range 2000–11,000 sec−1, the Bingham plastic model fitted slightly better. Since the high shear rate range was obtained using the capillary tube viscometer, it was concluded that great care must be exercised when scaling up from capillary tube data to pipeline installations, in which the wall shear rate rarely exceeds 500 sec−1. The dispersed kaolin suspensions were essentially Newtonian, but at the highest solids concentration a measurable degree of shear‐thickening behavior was observed. Results for turbulent flow of the flocculated material are in good agreement with those obtained for similar systems by Kemblowski and Kolodziejski (1973), who have already shown that Dodge and Metzner's equation (1959) for the friction factor of a power law material is not applicable.
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83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams
83.50.-v Deformation and flow

Tensile Behavior of Power‐Law Fluids Containing Oriented Slender Fibers

J. D. Goddard

J. Rheol. 22, 615 (1978); http://dx.doi.org/10.1122/1.549493 (8 pages) | Cited 2 times

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A summary is given of certain theoretical predictions of the tensile stress in suspensions of oriented rigid fibers in nonlinear materials exhibiting fluidlike power law shear behavior. The theory is compared with experimental creep data of Street (1971) for a lead matrix containing phosphor‐bronze fibers, and also with the extensional flow data of Chan et al. (1977) for polymer melts containing chopped glass fibers. In the first instance, the agreement is satisfactory, whereas in the latter it is only qualitative, suggesting a need for further work.
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83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams
83.50.-v Deformation and flow

An Improved Rheometer Design Used to Measure Viscoelastic Properties of Polymer Melts

Robert V. McCarthy

J. Rheol. 22, 623 (1978); http://dx.doi.org/10.1122/1.549494 (19 pages)

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A fixture consisting of a bob and a special cup was developed to ease the charging of polymer melt to the gap of a concentric‐cylinder rheometer. Dynamic measurements with the improved rheometer for two polyolefins below melt temperatures were compared with results obtained on the Rheovibron and the torsion pendulum. Shear moduli were generated for polypropylene, polyethylene,and poly(vinyl chloride) melts by oscillating the bob in the axial mode at amplitudes effecting relatively large strain. Bob oscillations in the rotational mode were also investigated. The phase angles and complex shear moduli differed slightly for different modes of oscillation. At strains of 9%, the time‐temperature shift factor αT remained constant throughout the test‐frequency range for an isotactic polypropylene. However, αT increased with increasing frequency for strains of 98%. A time‐strain shift factor, αϵ, was found to satisfactorily superimpose polypropylene moduli data generated at high and low strain levels.
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83.85.Cg Rheological measurements—rheometry
83.10.Gr Constitutive relations
83.80.Rs Polymer solutions
83.80.Sg Polymer melts

Turbulent Drag Reduction by Injection of Fibers

R. S. Sharma, V. Seshadri, and R. C. Malhotra

J. Rheol. 22, 643 (1978); http://dx.doi.org/10.1122/1.549495 (17 pages)

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Drag reduction in turbulent pipe flow by means of boundary and centerline injection of long hairlike fibers has been investigated. Experiments have been conducted at various main flow Reynolds numbers as well as at various injection rates of the fiber suspensions. The occurrence of drag reduction was observed even with a trace quantity of the fibers. Comparison of the two modes of fiber injection indicates that elongated fibrous elements are more effective as drag reducers when they are present in the outer region of the turbulent core. Measurements of the mean velocity profiles with both modes of injection indicate that the drag reduction can be attributed to a reduction in the momentum transfer ability of the suspensions in the turbulent core.
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83.60.Wc Flow instabilities
83.60.Yz Drag reduction
47.60.-i Flow phenomena in quasi-one-dimensional systems
83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams

Notes: On the Swelling of Extruded Plane Sheets

K. R. Reddy and R. I. Tanner

J. Rheol. 22, 661 (1978); http://dx.doi.org/10.1122/1.549499 (5 pages) | Cited 1 time

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Abstract Unavailable
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83.50.Jf Extensional flow and combined shear and extension

Abstracts from the Journal of the Society of Rheology, Japan

J. Rheol. 22, 667 (1978); http://dx.doi.org/10.1122/1.549503 (2 pages)

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Abstract Unavailable
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83.00.00 Rheology
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