A penalization-based strong partitioned coupling with application to cavitation-induced damage

Abstract

A novel strong partitioned coupling strategy is developed in order to address Fluid–Structure Interaction (FSI) problems. The Brinkman penalization method is adopted to model the deformable fluid–solid interface on a fixed Cartesian grid. Originally designed for single-phase flows and rigid bodies, the penalization method is extended to compressible multiphase flows and deformable walls. This numerical model is applied to the analysis of cavitation-induced damage at the microscopic scale, focusing on the shock-induced collapse of a single bubble near an elastoplastic material. We examine the effect of initial bubble–wall distance on wall pressure, material damage and permanent wall deformation (i.e., cavitation pit). This parametric study is conducted for different material yield strengths. Both pit depth and area increase rapidly as the bubble–wall distance and yield strength decrease. Whereas closer bubbles generate a deep, circular pit, more distant bubbles can produce a shallower, annular pit. The effect of FSI coupling is thoroughly analyzed across all parametric configurations. Wall deformation results in the damping of wall pressure, leading to differences in material damage between weakly and strongly coupled simulations. At the moment of impact, the damping of wall pressure is initially governed by the ratio of the acoustic impedances of the fluid and solid media. It is then further amplified locally by plasticity or, more generally, in regions of higher deformation. A small reduction in wall pressure leads to a much more significant damping in both pit depth and pit area. While the decrease in wall pressure is locally affected by material deformation, the change in pit size remains approximately constant for all configurations.