Surface Containing of Polymer Solutions and Pulsative Ejection

Abstract

THE possibility that polymer solutions tend to adhere to solid surfaces was examined by Kowalski¹, who ejected polymer solutions in pulses into a pure water boundary layer. It was found from the signal registered by a hot film sensor near the wall that the effect of polymer ejection persisted between ejections. This led Kowalski to suggest that a reduction in the quantity of additive for drag reduction might be achieved by adopting pulsed instead of continuous ejection. In a discussion¹, Fabula questioned Kowalski's results by pointing out that the period of signal persistence was about the same as the time required for the polymer solution to advance from the ejection slot to the sensor, and that entanglement of the polymer chains of the ejected, highly concentrated polyethylene–oxide solution might change the apparent character of the turbulence sensor.