Time scale and molecular weight distribution contributions to dilute polymer solution fluid mechanics

Experimental results on drag reduction in pipe flow, pitot tube errors and polymer degradation are presented to support a thickened sublayer model for dilute polymer solutions. The proposed model exhibits onset when the flow time scale equals the polymer time scale and increased drag reduction, degradation or pitot tube error as increased fractions of the polymers in the distribution are stretched by the flow. Eventually a limit is reached when the measure of increased sublayer thickness or increased effective viscosity in a pipe flow core reaches a limit due to entanglement of stretched molecules. The model correlates well with the experimental data.