摘要:

We discuss the application of a recently developed theory of multiphase mixtures to fluid‐saturated granular materials. The theory includes the incompressibility of each phase, but unlike other theories of the type, does not require pressure equilibrium between the phases. We do a theoretical study of the motion of this material in a viscometric simple shearing apparatus. It is shown that simple shearing generally does not occur. Typically, in the vicinity of a boundary, if the solid volume fraction is low, a layer of high shear rate occurs, while if the solid volume fraction is high, a ‘‘locking’’ phenomenon occurs. Otherwise, there is a tendency for particles to accumulate in regions of low shear rate.

ISSN:0148-6055    

DOI:10.1122/1.549894

出版商:The Society of Rheology    

年代:1986

数据来源: AIP

摘要:

Slip of a polymer as it flows through a conduit has been modeled by applying the concept of junctions at the conduit/polymer interface as well as in the bulk of the polymer fluid. This model has been combined with a kinetic equation describing a reaction, to which activation rate theory applies, between bonded and free macromolecules at the interface. The result is a prediction of the temperature dependence of wall slip velocities. The prediction was found to be consistent with published data for an ethylene‐propylene copolymer. It was also found that at constant temperature a power‐law relation provides a good description of the dependence of wall slip velocity on wall shear stress.

ISSN:0148-6055    

DOI:10.1122/1.549888

出版商:The Society of Rheology    

年代:1986

数据来源: AIP

摘要:

This paper deals with the problem of evaluating material elasticity through measurements of a material function such as the non‐Newtonian viscosity. A brief summary is provided between relations involving several material functions. In particular, two methods for predicting the primary normal stress coefficient from the steady shear viscosity are examined in detail. These methods are due to Bird, Hassager, and Abdel‐Khalik and to Wagner. Experimental data are presented involving test fluids such as polymethyl methacrylate solutions, polystyrene solutions, and polyacrylamide solutions. Finally, a relation between the shear viscosity and the primary normal stress coefficient is discussed using the concept of the finitely extensible bead‐spring chain model.

ISSN:0148-6055    

DOI:10.1122/1.549889

出版商:The Society of Rheology    

年代:1986

数据来源: AIP

摘要:

Although human red blood cell (RBC) suspensions exhibit viscoelastic behavior, the relations between this behavior and the viscoelastic properties of individual RBC are not well defined. Using an oscillatory Couette viscometer (oscillatory frequency 0.01 to 1.0 Hz, amplitude ±1°), we have measured the viscous (η′) and elastic (η″) components of the complex viscosity at 25°C for cells suspended in buffer at 80% hematocrit. Control RBC were compared to cells which had known alterations in their viscoelastic properties: (1) heat‐treated cells; (2) age‐separated cells; (3) cells in nonisotonic media (up to approximately 30% volume change). All suspensions exhibited decreases in η′ and η″ with increasing frequency, although the differences between altered cells and controls did not vary strongly with frequency. Suspensions of heat‐treated and maximally shrunk cells showed the greatest changes in viscoelasticity compared to controls: for heat‐treated cells, η′ was raised by 44% on average and η″ was raised by 67%; for maximally shrunk RBC, η′ was raised by 210% and η″ by 160%. Old cells showed slight increases (∼17%) in both components of the complex viscosity, but only minimal changes in viscoelasticity were noted for swollen RBC and young cell suspensions. Use of a Kelvin‐Voigt solid model indicated that the elastic component could not be entirely attributed to the RBC membrane elasticity but that the viscous component was probably dominated by the RBC membrane viscosity; a modified model, incorporating an additional elastic element, allowed the suspension elasticity to be better correlated with the known changes in cellular properties.

ISSN:0148-6055    

DOI:10.1122/1.549890

出版商:The Society of Rheology    

年代:1986

数据来源: AIP