High molecular weight polymers, drag

Due to difficulties in measuring the zero-shear viscosity of such high molecular weight polymers, and thus deducing the monomeric friction coefficient from Graessley s uncorrelated drag model [43], the following equation adapted from the modified Rouse theory has been applied [8]. 

Drag reducing additives are used by pipeline companies to increase the volume of product they deliver. These high molecular weight polymers reduce turbulence in fluids flowing in a pipeline. This can increase the maximum flow rate by up to 40%. When the additive modified product passes through a pump, the additive is broken into smaller molecules that have no effect on product performance in engines. 

Hydrodynamic drag reduction is an unusual effect involving macromolecules in a turbulent flow for very dilute solutions, the resistance to flow can be reduced compared to that of the pure solvent. Indeed, the presence of high-molecular-weight polymer chains can produce large levels of drag... 

Cowan, M.E., Garner, C., Hester R.D. and McCormick, C.L. (2001) Experimentally determined drag reduction efficiency and extensional viscosity of high molecular weight polymers in dilute aqueous solution. J. App. Poly. Sei., 82, 1222-1231. 

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