Experimental investigation on flow-induced vibration suppression by drag-reducing polymers

The polymer drag reduction in turbulent flow has been extensively studied for decades, with both commercial applications and fundamental implications. It is widely acknowledged within the scientific community that polymers primarily act by suppressing turbulent fluctuations, thereby significantly reducing flow resistance. Thus, the present work explored the potential of drag-reducing polymers to suppress flow-induced vibration by measuring the acceleration level of the fixed outer cylinder in a concentric rotor device. Maximum vibration suppression (Δ) of 7.54 dB and maximum drag reduction of 41.88% were achieved. The effects of Reynolds number (Re), polymer concentration, and molecular weight on the vibration suppression level and the time-dependent decay were all investigated. A distinct peak in vibration suppression level when Re = 75 990 was observed across all tested cases, attributed to the intrinsic properties of the flow-induced vibration in the rotor device. The vibration suppression, together with the drag reduction, decayed over time due to mechanical scission, with the Kohlrausch-Williams-Watt function quantitatively modeling the temporal behavior effectively. Notably, the vibration suppression diminished more slowly than the corresponding drag reduction. Moreover, solutions with the highest concentration or the largest molecular weight exhibited the best vibration suppression and drag reduction efficiency under both the successively increasing Re testing and the degradation testing. This dual suppression effect highlights the potential of drag-reducing polymers in simultaneously mitigating flow-induced vibration and energy loss.