Effectiveness of a drag reducing polymer: Relation to molecular weight distribution and structuring

Solutions of partially hydrolyzed polyacrylamide were degraded by intermittent circulation through a large pump in a turbulent flow loop. Measurements of pressure drop, fluid turbulence, molecular weight distribution, and viscosity were made. Rheo-optical studies were also carried out to explore the propensity of solutions to form structures under simple shear flow. Degradation was not accompanied by significant changes in the molecular weight distributions. This observation suggests that, for the system studied, clusters or aggregates of polymers have a more important effect on the turbulence than individual molecules. Therefore, degradation occurs by the destruction of these clusters. This result is consistent with the observation that larger drag reductions are realized by the injection of concentrated polymer solutions into a water flow.