Void Fraction Influence Over Aqueous Foam Flow: Wall Shear Stress and Core Shear Evolution

Abstract

In this study, the two main transport characterization problems of the foam flow are studied: foam flow stability, through the evolution of the velocity at the core of the foam, and rheology, with the study of the wall shear stress over the lateral walls, for different void fractions. The same velocity profile (block flow, mean velocity 1.75 cm/s) is imposed to the foam flow, at the inlet of the channel, for several void fractions (air/water relation) going from 55 to 85 %. Later on these ones are passed through a singularity (fence) to study the different behaviours induced by the particular properties of each case. The velocity fields, the lateral liquid film thickness and the lateral wall shear stress fields are obtained and compared with one another to comprehend and remark the difference in such a complex flow. The results show that as we move closer to very dry foams the shear at the foam core increases and its velocity becomes higher. However, the wall shear stress at the lateral wall does not present big deviations from one void fraction to the other.