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

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.10841183118

Drag reduction in polymer solutions based on splash visualization

The drag-reduction phenomenon is produced when very small amounts of some substances such as high-molar-mass polymers are dissolved in a solvent. In this paper some aspects of drag reduction were studied through the observation of the liquid deformation due to the impact of a droplet against a shallow surface using aqueous solutions of poly(ethylene oxide). The presence of polymer leads to a change in the splash morphology, mainly for the Rayleigh jet. The amplitude of the Rayleigh jet is highly sensitive to the concentration and molar mass of the polymer and can be used to determine the percentage of the drag reduction.33224224

Effects of Congo red on the drag reduction properties of poly(ethylene oxide) in aqueous solution based on drop impact images

The presence of very small amounts (ppm) of high-MW polymers in 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 MW, but also on the flexibility of the macromolecular chain. The Toms effect can be studied through the images of the structures produced after the drop impact against shallow solution surfaces. The splash structures composed of crown, cavity, and Rayleigh jet are highly dependent on the elongational properties of the solution. This work presents the effects of Congo red on the drag reduction properties of poly(ethylene oxide) in aqueous solutions through the analysis of splash structures. Results obtained in this analysis indicate that Congo red molecules act as physical cross-linking agents, decreasing the polymer elasticity and its drag reduction capacity. It was observed that the maximum height of the Rayleigh jet can be used as a sensitive parameter to the complexation between the dye and the polymer molecules.2026113151132