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Mechanical degradation of dilute solutions of polyethylene oxide (PEO) viachain scission was investigated within a turbulent pipe flow. Comparisons ofthe drag reduction performance with and without degradation were made bymatching the onset of drag reduction conditions, which has been shown for PEOto be related to the mean molecular weight. The bulk flow behavior of both thedegraded and non-degraded samples were generally consistent with trendsobserved in the literature, but a subset of conditions showed significantdeviation in the slope increment (drag reduction performance) between thedegraded and non-degraded samples. When they deviated, the degraded sampleswere consistently more efficient than the non-degraded samples even though theyhad the same mean molecular weight. The deviations were shown to scale with thenormalized difference between the initial and final molecular weights. Thecurrent data and analysis as well as the literature suggests that thedeviations in the polymer performance (slope increment) are related to changesin the molecular weight distribution. More specifically, the improvedperformance of the degraded samples relative to the non-degraded ones at themean molecular weight of the degraded sample indicates an excess of longerpolymer chains since the higher chain fractions in a degraded solution moreeffectively control the flow properties when within a certain degree ofdegradation and Reynolds number.

Drag Reduction Performance of Mechanically Degraded Dilute Polyethylene Oxide Solutions