摘要:

Following the foregoing work, extrusions in the cone were studied for highly filled suspension (HSF) of the kaolin‐water system including additive. By the visualization, the slip line was observed within the HFS, instead of the wall slip reported in the previous paper. In the cone, only one slip line was observed with a fixed boundary condition. Therefore, the direct analysis for slip can be applied different from the usual slip line analysis. The ordinary differential equations for slip angle, η, and mean principal stress, σm, were solved directly with the boundary condition as function of radius,r. Observed slip lines agreed well with the theory. The extrusive pressure calculated by integrating the stress component of the extruding direction along the slip line also agreed well with the corresponding piston load. Thus, the present method was useful.

ISSN:0148-6055    

DOI:10.1122/1.550657

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

The motion of a rigid cylindrical particle freely suspended in a two‐dimensional channel flow is studied numerically at low Reynolds numbers. The particle is assumed to be an elliptic cylinder or a doublet consisting of two equal‐sized circular cylinders held in rigid contact. The Stokes equations for the suspending fluid are numerically solved with a finite element method for an estimate of the longitudinal, lateral, and angular velocities of the particle at conditions of zero force and zero torque on the particle. Using the velocities obtained, the trajectories of the particle are determined for various initial configurations. The particle is found either to tumble or to oscillate cyclically, depending on the particle size/channel width ratio, particle shapes, and initial conditions. In the former case, both of the elliptic cylinders and doublets rotate continuously in one direction during one period, which is well approximated by so‐called Jeffery’s solutions for a spheroid in unbounded simple shear flow. In the latter case, the particle oscillates in rotation, accompanied by a periodic sidewise drift. The sidewise drift of doublets is about the center plane of the channel, while the mean lateral position of elliptic cylinders is either on or off the center plane.

ISSN:0148-6055    

DOI:10.1122/1.550658

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Steady viscous flow and dispersion properties of aqueous suspensions containing monodispersed silica microspheres of 0.9 μm were studied with special emphasis on the effect of PVA addition as a function of pH. Larger amount of PVA adsorption, observed at lower pH, always favored better dispersion and lower apparent viscosity. An apparent median particle size of the flocs in the stagnant suspension was mainly dominated by electrostatic repulsion and accordingly by pH. While the zeta potential was determined solely by the surface species of the particles coated with either Al2O3or ZrO2, silica substrate was suspected to affect the adsorption behavior of PVA on the silica particles, coated particularly by Al2O3.

ISSN:0148-6055    

DOI:10.1122/1.550660

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Dynamic viscoelasticity is measured for threadlike micelles from cetyltrimethyl‐ammonium bromide (CTAB) in aqueous sodium salicylate (NaSal) solutions at temperaturesT=25, 33, 40, and 50 °C. The CTAB concentration of the solutions is fixed atCD=0.01 M and a ratio of NaSal concentrationCStoCD,CS/CD, is varied from 1 to 41. Effects of bothCS/CDandTon frequency dependence of storage and loss shear moduli,G’(ω) andG‘(ω), are described in this paper in detail. Characteristic features of this micelle system may be summarized as (1) at 25 and 33 °C, the steady viscosity η and the mechanical relaxation time τMboth show a minimum atCS/CD∼4 that is followed by a maximum atCS/CD∼10 asCS/CDincreases. (2) The η and τMmonotonically decrease with increasingTin the range ofCS/CDfrom 1 to 20, but the maximum itself gradually disappears asTincreases. (3) The steady state complianceJeis independent ofTand decreases at lowerCS/CD. A rapid increase inJeis observed at higherTandCS/CDends. (4) An additional viscoelastic relaxation process is observed at the high frequency side. This mode appears in the same ω range independent of the salt concentration and exhibits theTdependence such as a type of the local friction factor, ηS/T. The discussion is mainly devoted to the applicability of a couple of models proposed so far.

ISSN:0148-6055    

DOI:10.1122/1.550662

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Non‐Newtonian characteristics of boundary layer flow passing a flat external surface with zero incident angle were studied using Phan‐Thien Tanner (PTT) type constitutive equation with the network theory. Consideration is given to the shear thickening and the shear thickening–thinning characteristics of fluid in the flow problem. The Von Karman integral equation is solved numerically in order to obtain the boundary layer thickness and associated friction coefficient. Two important parameters in the network theory, the segment number and chain slippage parameter, are discussed to investigate their effects on the boundary layer characteristics. The calculated results indicate that there are large jumps of boundary layer thickness at the leading edge of the plate for small slip parameters when the effect of normal stress is not included in the calculation. On the contrary, the jumps are eliminated, particularly for smaller Reynolds number, with the inclusion of the effect of normal stress.

ISSN:0148-6055    

DOI:10.1122/1.550663

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Normal force is measured which is generated in the flow between two rollers, one rotating and the other fixed. Aqueous glycerin solutions are used as Newtonian fluids, and dilute solutions of polyethylene oxide (PEO) and polyacrylamide (Separan) are used as viscoelastic fluids at concentrations of 50–1000 ppm in weight. The force measured for viscoelastic fluids is larger than that for Newtonian fluids. The normal force for Newtonian fluids is evaluated by applying the Cameron’s theory with the Reynolds equation and the half Sommerfeld condition. It is found that the calculated force agrees well with the experimental result. The normal force for viscoelastic fluids is predicted using the same assumptions as for Newtonian fluids except the constitutive equation of Coleman–Noll. The predicted expression is in good agreement with the present experimental result for dilute PEO solutions but roughly agree with the data for nondilute PEO and Separan solutions.

ISSN:0148-6055    

DOI:10.1122/1.550664

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

The viscosities of liquid dairy foods were measured in a slit rheometer with gap spacings as small as 34 μm. Large positive deviations from the true flow curve and an approach to a constant stress were observed below a critical rate in each material studied. This behavior is indicative of probable agglomeration and ‘‘bridging,’’ most likely in the entrance to the dye. In all cases mean particle sizes were an order of magnitude smaller than the slit.

ISSN:0148-6055    

DOI:10.1122/1.550667

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

The effect of physical aging on excess enthalpy has been investigated for the amorphous poly(ethylene terephthalate) (PET) glasses prepared by both means of quenching the melt into liquid nitrogen (type I) and casting the melt on a rotating metallic roller at 10 °C (type II). The relaxation toward the equilibrium of the enthalpy, monitored by a differential scanning calorimeter (DSC), is described by a relaxation fraction of the excess enthalpy φ as a function of aging time and temperature. On the physical aging in the two PET samples, a plot of φ against log tagives an essentially straight line for the PET I sample, and the plot for the PET II sample can be divided into three distinct regimes with increasing log ta: a short‐time regime where φ linearly decreases with log ta, a middle‐time regime where φ takes an almost constant value, and a long‐time regime showing a secondary decrease in φ. When the PET II is aged at 60–70 °C, two endothermic peaks in a DSC scan arise in the middle and the longer regimes of the aging time. The peak positions as well as their magnitudes considerably vary with the aging time. These results for the PET II suggest that polymer‐chain rearrangement during the physical aging process is a dissipative process which results in nonhomogeneous glassy structures consisting of low‐ and high‐enthalpy regions.

ISSN:0148-6055    

DOI:10.1122/1.550668

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Finite difference solutions and observations have been presented for the flow of dilute suspensions of rigid, high aspect‐ratio fibers in Newtonian fluids through a 4:1 tubular contraction. The effect of flexibility of particles on the flow fields is also discussed from comparison of their configuration and entry flow patterns between rigid fiber suspensions and flexible molecule systems. For rigid fiber suspensions, the main flow patterns become nearly conical and the corner vortex length is almost independent of flow rate under the Reynolds number less than 0.1. On the other hand, for flexible molecule systems, the corner vortex rapidly grows with an increase in flow rate and the wine‐glass shaped flow with the convex vortex boundary also presents a striking contrast to the fiber suspension flows. Therefore, full discussion of the change in fiber or molecule configuration during flow seems most significant to understand the energy flow kinematics. Further, the computed stress fields clearly indicate that entry flows of rigid fiber suspensions can also exhibit the stress relief phenomenon due to vortex enhancement, which was observed for polymer liquids: the increase in the normal stress difference around the center line near the entrance of the contraction can be suppressed.

ISSN:0148-6055    

DOI:10.1122/1.550669

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Zero shear viscosities η0were measured for toluene solutions of ten fractionated poly(n‐hexyl isocyanate) (PHIC) samples from dilute regime to concentrated isotropic regime. PHIC is a semiflexible polymer with the persistance lengthq=37 nm in toluene. For six PHIC samples with the molecular weight less than 14×104, the dependence of η0on the polymer concentrationcdid not obey any power law, while for the higher molecular weight samples,n0was almost proportional toc3.2in a highcregion. At fixedc, η0was almost proportional toM4vin a highMvregion (Mv: viscosity average molecular weight). These concentration and molecular weight dependences are distinct from not only those for flexible polymer solutions but also those for much stiffer polymer solutions [e.g., schizophyllan (q=200 nm) and xanthan (q=120 nm)]. The results of η0for PHIC solutions obtained were compared with Teraoka–Hayakawa’s theory for rodlike polymer solutions and with our fuzzy cylinder model theory for semiflexible polymer solutions. The former theory agreed with the experimental results only for the second lowest molecular weight sample with a rodlike conformation. On the other hand, the latter theory succeeded in explaining quantitatively the results for seven samples with intermediate molecular weights. Neither of the theories agree with the data for the lowest molecular weight sample, because they neglected the intermolecular hydrodynamic interaction which becomes important for short chain polymers. For the two highest molecular weight samples, the fuzzy cylinder model theory failed to describe the η0data, because of some additional flexibility effect which is not cleared yet.

ISSN:0148-6055    

DOI:10.1122/1.550670

出版商:The Society of Rheology    

年代:1995

数据来源: AIP