Séminaire

Vendredi 2 Juin 2023 à 11h00.

How foam is spread on a substrate

''Liquid foam is ubiquitous in our everyday life, such as foods, beverages, detergents and cosmetics. Although foam consists only of liquid and air bubbles, it has a variety of unique properties. For example, foam exhibits some elastic response to weak stress and weak strain, but to large strain, foam deforms and flows macroscopically with rearrangements of air bubbles. These macroscopic behaviors can be observed when washing the bodies or dishes. While this is a common situation and the dynamics and mechanism of the spreading of liquid on a substrate have been studied for decades, that of foam has not yet been clarified. Here, we focus on how a foam is spread by a rigid plate on a low wettable substrate. Differently from simple liquid case, three distinguishable spreading patterns were observed with increasing the spreading velocity: homogeneous spreading (pattern 1), non-spreading (pattern 2), and slender spreading (pattern 3). We fabricated the spreading pattern diagram from experiments where the gap height, confinement length, amount of the foam, and wettability of the substrate were independently varied. Furthermore, we succeed to describe the border between patterns 1 and 2 theoretically. In this talk, we will show the dynamics of each pattern and theoretical approach to elucidate the dynamics and the borders between patterns. *This work is done with Masaya Endo and Rei Kurita.''