Multiscale analysis of liquid foam structure using X-ray tomography

Liquid foams are dispersions of closely packed gas bubbles within a liquid phase. They are commonly encountered in daily life, such as in food and cosmetics, and are extensively used in industry due to their unique mechanical properties, exhibiting both solid-like and liquid- like behavior. However, predicting the rheological behavior of liquid foams remains a challenge due to the complex interplay of elementary flow events, which consist of local bubble rearrangements. The main difficulty lies in the experimental observation of structural evolution. Standard rheological tools provide only the macroscopic mechanical response of the material and lack the spatial resolution required to capture flow heterogeneities and structural changes.In this thesis, we demonstrate the capabilities of fast X-ray tomography to monitor the local structural evolution of liquid foams and to extract fundamental quantities such as flow, elastic stress, and plastic activity fields, resolved down to the scale of individual bubbles. Each of the appended papers present a different aspect of liquid foam flow: local elementary rearrangements (Paper A), continuous flow through a complex geometry (Paper B), and transient relaxation after flow cessation (Paper C). In addition to these scientific contributions, the image analysis method developed for this work is documented (Paper D) and shown to be generalizable to other cellular systems, such as bread (Paper E).