Wet Foam Flow in Horizontal Square Duct and Through Singularities

In this study, we characterize experimentally, the behavior of a wet foam flow along a square channel and through some singularities (an enlargement and a fence). The enlargement characteristics are a square section 21×21 mm2 at the upstream and a rectangular section of 21 × 42 mm2 at the downstream, for an aspect ratio of 0.5. As for the fence, it presents a height of 10 mm, a width of 5 mm and an inclination at its point of 45°. Experimental data were obtained in order to well understand the singularity effects over the foam flow and its texture in the immediate vicinity of this latter. The experimental investigation is focused into finding the wall shear stress and the liquid film which links the duct walls to the foam flow. The properties of the foam and the influence of this phenomenon might have an important role. We try to relate the wall shear stress obtained experimentally to determine the rheological properties of the foam. The use of different experimental devices and measurement techniques allow the comprehension of physical phenomena aspects that govern the foam structure. The PIV method gives the dynamics of the wet foam including the velocity fields near the walls. These ones are experimentally obtained from a series of instantaneous snapshots that will capture the bubbles movement. The innovative use of the polarographic method hands the measurements of the mass transfers, from which wall shear stress between the foam flow and the Plexiglas walls of the channel can be determined. The mass transfer measurement technique is based on a polarography method, by measuring the redox reaction controlled by the convection and diffusion phenomenon. The conductimetry technique, based on the measurement of the electric resistance in a liquid volume, allows the accurate perception of the liquid film thickness formed between the foam flow and the walls. The static pressure losses are directly obtained by the measurements taken from a series of pressures taps placed in the bottom wall of the channel. This parameter will allow the determination of the foam flow behavior. It is taken into consideration a one-dimensional flow, meaning that the established flow behaves as a piston or move as a bloc, with a foam velocity of 2.3 cm/s. All experiments lead to determine the general tendency of the foam flow structure along the square channel and the singularities, including its rheology behavior and drainage ability.Copyright © 2013 by ASME