Study of hydrodynamic drag reduction polymericsolutions based on the drop impact images

Author(s)

Melissa Inger Alkschbirs

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2004-07-12

Examining board members

Edvaldo Sabadini; Marcos Pinoti Barbosa; Antonio Carlos Bannwart; Fred Yukio Fujiwara; Maria Isabel Felisberti

• Advisor: Edvaldo Sabadini; Marcelo Ganzarolli de Oliveira

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, termed as the Toms Effect, was studied using images of the impact of a small drop against shallows liquid surfaces, both liquids containing a drag reducer agent. After the impact a crown and a cavity are created and the collapse of these structures impels a liquid column, named as Rayleigh jet. This phenomenon is termed splash. The amplitude reached by the Rayleigh jet was used to estimate the energy of the drop stored in the liquid; therefore, the maximum height of the jet allow us to determine the percentage of drag reduction. The results were discussed in terms of different parameters such as polymer concentration, molecular weight in the poly(ethylene oxide), PEO, the most efficient drag reducer agent in aqueous system. The splash in aqueous polymeric solution is dominated by the elongational viscosity and therefore, the polymer relaxation time has an important role in the process. We consider that the main contribution of this work to the drag reduction field is the new approach proposed to investigate this old hydrodynamic phenomenon (AU)