Surface wettability effects on the behavior of air bubbles injected into water flows

Abstract

The practice of injecting air bubbles into the boundary layer of external viscous fluid flows has been studied in recent decades as a viable method of reducing frictional drag. This outcome is desired by many industries, marine industry in particular, as an approach to diminish fuel consumption and pollution of ocean-going vessels. Tremendous drag reduction has been observed by employment of air injection in model-scale experiments, yet adoption at the industrial scale has been quite limited. A large reason for this hesitation is the lack of control over the air bubbles as they travel along the solid surface. Air bubbles tend to migrate from the solid surface a short distance from where they are injected and have small effect on frictional drag reduction over large length scales. There is also a lack of control over air bubble size and shape in the streamwise direction. A solution to these setbacks must be reached before industrial-sized applications may be pursued.