Drag reduction in aqueous poly(ethylene oxide) solutions based on drop impact images

Abstract

The presence of very small amounts (ppm) of high molecular weight polymers in a solution produces high levels of drag reduction in a turbulent flow. This phenomenon, often termed as the Toms Effect, is highly dependent not only on molecular weight (MW) but also on the flexibility of the macromolecular chain. This paper describes the effects of poly(ethylene oxide) MW, concentration, and chain compaction on the impact structures produced during collision between a droplet against a shallow liquid surface (splash), both liquids containing the polymer. The impact energy stored in the splash structures (composed of crown, cavity, and Rayleigh jet) was estimated using a simple model and some morphological parameters obtained from instantaneous images of the splash. It was observed that the height of the Rayleigh jet, a liquid column produced from the collapse of the crown and the cavity, is highly sensitive to the elongational viscosity of the solution.