Drag-reduction effectiveness

In the extensive literature on polymer drag reduction, it has occasionally been reported that a continuous thread of a high-concentration polymer solution injected into the axis of a pipe produces a drag-reduction effect on the water flow in the pipe [856]. The thread seems to persist through the length of the pipe and little, if any, diffusion of polymer to the walls of the pipe is apparent. 

Kim, O.K., Little, R.C., and Ting, R.Y. "The Correlation of Drag-Reduction Effects with Polymer Intrinsic Viscosity," J. Colloid Interface Sci.. 1974, 47(2). 

The fields of application listed below (Tab. 1) are only a few examples to indicate the potential for employing the drag reduction effect. 

The first reports on the drag reduction phenomenon are found in publications by Blatch (1906), Forrest (1931), as well as by Brautlecht (1933), who measured the flow behaviour of paper pulps. In independent studies made by Mysels (1949) and Toms (1948) this phenomenon was observed in the turbulent flow of gasoline in pipes when aluminum soaps were added and, in Toms experiments, when polymethylmethacrylate in monochlorobenzene was used. The reduction of friction is therefore often termed the Toms effect . This flow behaviour is also known in the literature as the Non-Newtonian- , visco-elastic- , Texas- or Texas-Toms-effect , due to the contributions made by Texan researchers. It is also more generally known, and this term will be used in this paper exclusively, as the drag-reduction effect of flow additives. 

Fig. 2. The Alaska pipeline, one of the most significant large-scale technical examples of the benefits to be gained from the drag reduction effect. Over a distance of 1287 km, polymer is injected approximately every 100 km at a concentration of 5-25 ppm...

Other possibilities of calculating the drag reduction effect are the following ... 

The flow enhancement effect is completely suppressed in the presence of trivalent cations. Even at the preparation stage for aluminium sulfate (Al2(SOi)3), the polymer is precipitated at a concentration of c = 5 ppm the flakes thus formed can be clearly seen, suspended in solution. Consequently, no drag-reduction effect can be expected and the experimental solution behaves as a Newtonian fluid (Fig. 31). Therefore, it is likely that multivalent cations from complexes or ionotropic gels and that by exceeding a critical value they may precipitate out of solution. 

Fig. 32. Influence of M on drag reduction effect for nonionic polyacrylamide samples, d = 6.1 mm (data taken from Gampert, Wagner 1985)...

Deshmukh SR, Singh RP (1987) Drag reduction effectiveness, shear stability and biodegrada-dation resistance of guargum-based graft copolymers J Appl Polym Sci 33 1963... 

Hlavacek B, Rollin LA, Schreiber HP (1976) Drag reduction effectiveness of macromolecules Polymer 17 81... 

Hoyt JW (1971) Drag-reduction effectiveness of polymer solutions in the turbulent-flow rheometer a catalog J Polym Sci, Polym Lett 9 851... 

Reddy GV, Singh RP (1985) Drag reduction effectiveness and shear stability of polymer-polymer and polymer-fiber mixtures in redrculatory turbulent flow of water Rheol Acta 24 296... 

Fig. 1 Drag reduction effectiveness vs. polystyrene concentration in toluene, a good solvent. (From Ref...

A. N. Direct numerical simulation of viscoelastic turbulent channel flow exhibiting drag reduction effect of the variation of rheological parameters. J. Non-Newton. Fluid 1998, 79 (2-3), 433-468. 

Lin, Z. The effect of chemical structures of cationic surfactants or counterions on solution drag reduction effectiveness, rheology and micellar microstructure. Ph.D. dissertation. The Ohio State University, Columbus, OH, 2000. 

Broniarz-Press, L., Rozanski, J., and Rozanska, S., Drag reduction effect in pipe systems and liquid faUing film flow, Rev. Chem. Eng., 23, 149-245 (2007). 

Deshmukh, S. R., and Singh, R. R, Drag reduction effectiveness, shear stability and biodegradation resistance of guar gum-based graft copolymers, J. Appl. Polym. Sci., 33,1963-1975 (1987). 

Drag-Reduction effectiveness and resistance to the shear degradation... 

On this basis one can obtain additional information about the dependence of the friction drag reduction effect on the size of macromolecules. Let us, to this effect, use the results of ref. C4]. 

It may be concluded that by grafting polyacrylamide chains onto guargum backbone, highly drag reduction effective, shear stable and biodegradation resistant drag reducing polymers can be developed. 

Solution preparation is a complex problem and not very well understood. Recent experiments by Chang and Darby [1] and Oliver and Bakhtiyarov [2] indicate that the drag reduction effectiveness of partially hydrolyzed polyacrylamides increases with mixing time. At Arizona State University we have obtained similar results especially when the solvent is deionized water. On the other hand freshly mixed poly (ethylene oxide) (PEO) solutions give the most drag reduction. Impurities and ions present in v/ater also affect the polymers. In addition agglomerates of molecules may be present in the solution or can be formed by the flow. These solution difficulties are present in both aqueous and nonaqueous solutions. 

A linear theory of viscoelasticity is sufficient for obtaining a significant drag reduction effect qualitative arguments which assume that either or 14 depend on the kinematics of turbulent flows appear unnecessary (see, esp., Lumley (8)). 

Published results show that hydraulic transport of material has been found to be a technically feasible, enviromentally attractive and very economic method of transporting solid particles in different shape and size for short or long distances. The hydrotransport of solids in pipes is a particularly interesting possibility for the industrial applications of drag reduction effect. Despite intensive investigations of drag reduction its practical use for hydrotransport has only been treated in a few technical publications. 

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