Effect Of non-Newtonian Viscosity Research Articles

A Simple Approach to Evaluate Non-Newtonian Viscosity Effects in a Lubricating System

The working characteristics of a finite width slider bearing lubricated by a non-Newtonian fluid are computed. The analysis proposed here allows its performances to be evaluated by means of a pocket calculator. For that purpose, a computer code based on a finite element method is used. The program runs for different values of pertinent kinematical, geometrical and rheological parameters. The corresponding results are fitted by means of adequate analytical formulas, which are very easy to handle. The accuracy of these empirical formulas is investigated in several typical cases. The agreement with the numerical solution is proven to be satisfactory.

Two dimensional model analysis of flow behaviour of highly viscous non-Newtonian fluid in agitated vessel with paddle impeller.

A flow of non-Newtonian power law fluid in an agitated vessel with paddle impeller is obtained from numerical analysis based on a two dimensional flow model. The average shear rate obtained from the numerical solution coincides well with the experimental result for large-size impeller of d/D>0.7, and it is confirmed that the apparent viscosity is very useful in correlating not only power input but also shear stress distribution at vessel wall. The non-Newtonian viscosity profile in an agitated vessel depends remarkably on impeller dimension and scarcely at all on vessel dimension. This shows the usefulness of the concept of apparent viscosity proposed by Metzner et al. On the other hand, the velocity and vorticity profiles near the vessel wall can hardly be correlated with the characteristic velocity alone, because the flow pattern depends on the integrated effect of non-Newtonian viscosity in the flow region. These profiles show good similarity by using the appropriate correction factor.

The Mechanism of Reduction of Water Mobility by Polymers in Glass Capillary Arrays

Abstract Flow experiments with polymer solutions in arrays of glass capillaries with diameters of 2,5, and 25 microns have produced physical evidence of the mechanism by which polymers and polymeric gels reduce water mobility in porous media. The results indicate that polyacrylamides and polysaccharides reduce the permeability of straight glass polysaccharides reduce the permeability of straight glass capillary arrays by forming an adsorbed layer of polymer on the capillary wall that reduces the polymer on the capillary wall that reduces the effective size of the capillary. The effective thickness of the polymer layer on the glass surface was about 0.2 to 0.3 micron. The thickness was slightly less than the molecular diameter of 0.3 to 0.8 micron of the molecules in 1,200-ppm brine and was found to be independent to pore size for pores with diameters larger than three to four times the average molecular diameter of the polymer in solution. it was concluded that the reduction of water mobility by polymers in a porous medium, over and above the effect of increasing the viscosity, results form an adsorbed layer of polymer on the pore walls, and from mechanical entrapment in pore constrictions and small pores. It was shown that a previously reported sequential polyacrylamide-cation treatment method could polyacrylamide-cation treatment method could be repeated to achieve very large decreases in mobility to brine. The cross-linked layer established during the first sequence was three to five times more effective in reducing the pore diameter than the initial polyacrylamide layer. For example, the average thickness of the cross-linked layer formed with each sequence of particular polyacrylamide (19-percent hydrolyzed) was 1.5 microns, compared with 0.3 microns for the initial polyacrylamide layer. No mixing of polacrylamide and crosslinking solutions was required for this sequential system to be effective, since extensive flushing with water between the solutions in the sequence did not alter the results. Hence, it should not be necessary to propagate highly viscous solutions or gels through a reservoir to develop large residual resistance factors in depth with the sequential system. Introduction Investigators of polymer effects on water mobility in porous media normally have used outcrop sandstones, reservoir cores, glass bead packs, and sand packs, all of which have complex flow paths and surface characteristics that vary somewhat from sample to sample. As a result, it has been difficult to produce direct physical evidence of the mechanism by which polymers and polymeric gels reduce the permeability of these porous media, and researchers have postulated various mechanisms based on the combined interaction of polymer and geometry to explain the observed effects. We used fused-glass capillary arrays to investigate the mechanism of permeability reduction. The glass] arrays provided a means for determining effects of polymer in geometrically simple pores of the same polymer in geometrically simple pores of the same size as those in reservoir porous media; since they could be used repeatedly, the same geometry and surfaces were available for each test. The main purpose of this research was to provide direct physical evidence of how and where provide direct physical evidence of how and where polymers interact with surfaces of porous media. polymers interact with surfaces of porous media. We were primarily concerned with effects caused by polymer adsorption and retention remaining after polymer solutions had been displaced from porous polymer solutions had been displaced from porous media by water. Other aspects of polymer flooding, such as non-Newtonian viscosity effects, inaccessible pore volume, behavior attributed to pore volume, behavior attributed to viscoelastic properties of polymer solutions, salt concentration, pH, polymer molecular weight, and degree of hydrolysis, have been investigated previously in more conventional porous media. previously in more conventional porous media. Additional evidence is provided on how the combination polyacrylamide-cation treatment method,]composed of sequential injection of solutions of polyacrylamide and aluminum citrate, produces large polyacrylamide and aluminum citrate, produces large residual resistance factors to water and brine. This evidence provides a basis for tailoring in-situ polymer networks to the needs of a particular polymer networks to the needs of a particular reservoir SPEJ p. 130