Characterization of bubble mobility in channel flow with fibrous porous media walls

In composites processing, resin is introduced into a fibrous domain to cover all the empty spaces between the fibers. It is important to extract air bubbles from the domain before the resin solidifies. Failure to do so will entrap these voids in the final part, which is detrimental to its performance. Hence, there is a need to understand bubble motion in a fibrous porous domain in which the bubbles move with the resin in channels surrounded by fibrous walls. A rising bubble model is presented that consists of a single spherical void in a cylindrical axisymmetric two-phase domain of resin and air surrounded by porous media boundaries. The motion of a bubble in a channel flow with porous boundaries is modeled by replacing the walls with a slip velocity. Focus is on how the porous media permeability influences the bubble motion. A parameter called bubble mobility is defined as the ratio of bubble rise velocity to the resin free surface velocity. Results suggest that fabric permeability and fluid properties can be optimized to increase bubble mobility and ultimately lead to reduction in void content during composites processing. (C) 2013 Elsevier Ltd. All rights reserved.