Design of a mechanical system for the experimental study of the collapse of a granular column in water at rest : validation and flow measurements using imaging techniques

This thesis focuses on the study of granular media behaviors in water, aiming to contribute to their numerical modeling research. To achieve this, experiments are conducted on a commonly studied configuration known as the collapse of a granular column in water. The purpose of these experiments is to obtain analyzable recordings of the collapse. The paper is divided into two main parts. The first part focuses on designing a mechanical system specifically made for studying the aforementioned configuration. The limitations of former designs are identified, and new system requirements are established. Through testing, the final design is validated, providing a reliable mechanism for investigating granular collapse. The second part is dedicated to experiments and starts with a comprehensive description of the experimental setup including its limits and boundaries, providing insights for future research. The laboratory experiments are conducted at the \textsc{LEMSC} in UCLouvain, using a high-speed camera to capture videos. The resulting images are then analyzed using image processing methods with \textsc{python} and \textsc{Davis 8} software. A theoretical model based on Monsorno \textit{et al} is presented to understand the physical behavior of granular material in two-phase flows. Key parameters influencing the collapse are summarized. A parametric analysis of the collapse is conducted through five different aspect ratios, two types of sand, two initial volume fractions and whether or not the presence of a sand bed downstream. The results yield significant findings regarding the influence of these parameters. Comparisons are made between the experimental results and numerical simulations based on the proposed model. While there are good agreements in the final shapes of the deposits, differences in the temporal characteristics of the collapse are observed. The thesis concludes by highlighting the progress made in understanding granular media, while also emphasizing the need for further explorations and comprehension. The complex behavior of granular media still holds many unknowns. This thesis contributed to the existing knowledge by providing a range of experimental recordings that can serve as a foundation for future investigations in the field of granular collapse in water.