Weightless bubble lattices: A case of froth wicking

Abstract

In the absence of gravity drainage, froth wicking draws excess fluid onto a bubble lattice. Capillary forces only cause fluid transport; a moving front moves stably and without fluid fingering along a constant velocity bubble–fluid contact line. This percolation of fluid crawling up the lattice shows (1) fluid coverage on lattice borders varies linearly with available surface area (proportional to lattice perimeter); (2) fluid accelerates through regions or nests of high bubble density (number of bubbles cm−2). The development of nearly two-dimensional bubble lattices in variable gravity (step function between 0.01 and 1.8 times earthly gravity) are examined experimentally and a zeroth-order model for froth wetting is presented, which captures many of the principal observations. Possible applications for bubble lattices include adhesion casting of metals and separation of biological cells, bacteria, and particles.