REDUCTION OF DRAG IN TURBULENCE BY DILUTE POLYMER SOLUTIONS.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
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The object of this thesis was to investigate the drag reduction phenomenon in turbulent flow caused by random coiling macromolecules in dilute solution. In particular, this thesis was concerned with the relationship of drag or its reduction to the size of the coils and their concentration, of two kinds of polymers differing significantly in chain flexibility polyethylene oxide PEO, the more flexible, and polyisobutylene PIB, the less flexible. It was found that, within any given homologous polymer series, the ability of macromolecules to reduce drag improved drastically with increasing molecular weight. That is, the concentration of polymers in solution either in the absolute weight fraction or in the effective volume fraction required to yield a given percent drag reduction decreased rapidly with increasing molecular weight. It was further found that there always existed an optimum concentration for any given polymer system at which the observed drag reduction reached a maximum.