Index of content:
Volume 19, Issue 3, September 1975
19(1975); http://dx.doi.org/10.1122/1.549373View Description Hide Description
Shear‐Induced Thinning and Thickening of Raw Cement Slurries: Effect of Simple Ions and Polyelectrolytes19(1975); http://dx.doi.org/10.1122/1.549376View Description Hide Description
Additions of some polyelectrolytes intended to induce thinning of slurries sometimes cause the opposite effect. At a given level of ion concentration in the slurry water, increasing the amount of polyelectrolyte(sodium tripolyphosphate or sodium humate) additions caused inversion from shear‐induced thinning to shear‐induced thickening. The concentration of polyelectrolytes at inversion shifted towards lower values with reduced concentration of ions in the slurry water. A qualitative interpretation of the mechanism of the phenomenon is proposed, based on the effects of the structure of montmorillonite clays. These involve facilitating shear‐induced flow orientation (thinning) by polyanionic adsorption at the edges and chemically promoted shear‐induced breakdown of tactoids leading to thickening.
19(1975); http://dx.doi.org/10.1122/1.549377View Description Hide Description
A general method is suggested for classifying steady, isochoric elongational flows. A procedure is outlined to determine from experimental data the material functions which, as shown by Coleman and Noll, characterize incompressible simple fluids in steady elongational flows. For uniaxial and biaxial elongation, two possible definitions of these material functions are obtained. As an illustration, predictions for material functions are given for Lodge's rubberlike liquid constitutive equation.
19(1975); http://dx.doi.org/10.1122/1.549378View Description Hide Description
Both the theoretical and experimental results of the extension of a filament of viscoelastic material by surface forces are presented. The filament is horizontally supported on an inviscid substrate fluid and is drawn out by interfacial force effects. A momentum balance establishes the general shape of the viscoelastic filament geometry and 16 mm motion picture film provides specific data. The results establish that the flow is an unsteady extension and that the filament bulges and contracts due to the presence of inertial effects according to Coleman and Noll's 1962 prediction. Extensional viscosity is also discussed.
19(1975); http://dx.doi.org/10.1122/1.549379View Description Hide Description
The flow analysis network (FAN) method previously developed for die design is adapted to the problem of the cavity filling process in injection molding. The method is applicable to relatively narrow gap cavities of any shape. It permits the computation of the advancing front of melt at any time, as well as prediction of weld‐line location. The method was extended to nonisothermal flow in which solidification and “skin” formation during filling time was approximately accounted for. The nonisothermal analysis allows prediction of the possibility of a “short shot” situation. The analysis is applicable to any prescribed pressure or flow rate at the gate. Both can be arbitrary functions of time.
19(1975); http://dx.doi.org/10.1122/1.549380View Description Hide Description
Studies were made of neutrally buoyant suspensions of solid particles in steady flow through tubes. MicrowaveDoppler flowmeter techniques made it possible to investigate the moderate Reynolds numbers and high particle concentrations appropriate to many biological and industrial applications. The tubular pinch effect and the development of partial plug flow were observed independently at low concentrations and low Reynolds numbers, respectively. Both effects occurred together at simultaneously high concentrations and Reynolds numbers. For a given flow condition, the fraction of the tube consolidated in plug flow increases as either concentration or Reynolds number is increased.
19(1975); http://dx.doi.org/10.1122/1.549381View Description Hide Description
We present an analysis of the variation of interface position during the stratified two‐phase flow of two Newtonian fluids (1) between parallel plates and (2) through a circular tube. The analysis, which is based upon Reynolds lubricationtheory, predicts that the high viscosity phase pushes into and displaces the low viscosity phase during extrusion. The extension of the analysis to viscoelastic fluids is also considered. The theoretical predictions are in general agreement with experimental studies of interface shape in tubular side‐by‐side two‐phase stratified flow.
19(1975); http://dx.doi.org/10.1122/1.549397View Description Hide Description