Numerical simulations of bidimensional wet liquid foams flowing through complex geometries

Abstract

Owing to the inescapability of using foams in industry, technology, and engineering, researches that delve into their rheological behaviour are utterly significant, and the fact that foams share many rheological properties with granular materials, colloidal systems, and emulsions; has further enhanced this significance. Hence exploring the rheology of foams would cast light on a range of problems related to the rheology of the systems mentioned above. In this study, computer simulations are conducted to predict the behaviour of foams that flow in vessels of various geometries utilizing a modified version of the “Bubble model” on wet liquid foams, taking into consideration the inertial effects, the attractive interactions between bubbles and the shear in the thin intervening fluid layer between bubbles that are a small distance apart, in contrast to other previous similar studies. Notwithstanding disparities, the application of periodic boundary conditions instead of non-periodic boundary conditions has been gaining traction amongst the computational rheology community, due to less computational efforts and complexity that employing the former conditions requires. Perceiving the need to rectify this implementation of periodic boundary conditions on an ad hoc basis, a non-periodic boundary conditions ab initio imposition, a technique hitherto computational rheology studies have been void of its utilization; at the entrance and the exit of rectangular vessels is contrived to be introduced. Since one of the advantages of adopting this model is its flexibility in dealing with any shapes, it is adopted to simulate foam flow around square objects, without resorting to rounding their sharp corners, as it has been noted in all numerical experiments that address foams flow around obstacles with angular shapes; thus further perspectives on the behaviour of liquid foams flowing around other angular shapes would be highlighted. Moreover, noting the lack of numerical studies that investigate the interplay between a liquid and foam bubbles, a subject of significance in computer graphics, the flow of bidimensional foams partially filling a vertically positioned rotary drum, the lower half of which is filled with a liquid; is presented. Simulations of the foam flow around circular and square objects in rectangular channel and rotary drums, through two-sided rectangular and semicircular constrictions, in half-filled rotary drums are explored by virtue of velocity profiles, velocity field, topological rearrangements, interface deformation analysis, bubbles trajectories, texture tensor, drag force exerted by the flowing foam on the obstacles, and varying the strength of the attractive forces relative to the repulsive forces between bubbles. In this work, the parameters have been selected such that results from more detailed foam flow models are well reproduced. Accordingly, it is expected that, compared with previous similar works, investigating the influence of the chosen set of parameters on the resulting simulations would show that the present simulations are better. The author realizes that the parameter values used in computations conducted in this work are often different than those adopted in the studies that are referred to in this thesis that make it difficult to formulate direct conclusions. However, similar effect/s that can be observed in the aforesaid studies, even though the values of the parameters utilized are dissimilar to those used in these studies; are discussed and compared to the results acquired in this work. It is clear that more analysis should be done in the future to justify/verify this first glance impression.

Date of Award	2021
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Simon Cox (Supervisor) & Tudur Davies (Supervisor)