A structural basis for drag-reducing agents

✍ Scribed by C. A. Parker; A. H. Hedley

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 976 KB
• Volume: 18
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1974.070181120

✦ Synopsis

The various types of drag-reducing systems and their hydrodynamic shear degradation are briefly reviewed and some new measurements reported. The new measurements include the determination of the efficiency of drag reduction by a variety of systems ranging from fully flexible polymers, more rigid polymers, and asbestos fibers. These results, together with those of previous workers using fractionated polymers, show a good correlation between critical concentration and particle length. The results suggest that at the highest wall shear stress, the parameter governing the efficiency is the contour length of the particle, irrespective of its structure, stiffness, or diameter. At lower wall shear stresses, the shorter flexible molecules are less efficient, but the short rigid ones and the long flexible ones maintain their efficiency. The shear degradation of the systems was measured by repeated passages of the solution through the measuring apparatus at both high and low wall shear stresses. Drag reduction measured at low wall shear stresses is an extremely sensitive indicator of shear degradation of flexible polymers.