Fluid-immersed frictional contact of highly deformable solids in an Eulerian framework

Predicting how soft bodies collide, slide, and deform while immersed in a fluid remains challenging because solid mechanics, fluid dynamics, and contact must be resolved simultaneously. We present an extension to the Eulerian Reference Map Technique (RMT) that robustly handles frictional self- and multi-body contacts for arbitrary deformable solids immersed in a Newtonian fluid. The method retains one shared Eulerian velocity field and represents contact geometry by exploiting a single level set field, augmented by auxiliary grid fields that enforce normal contact and frictional responses, producing a unified and efficient formulation. We validate the method against established benchmarks: a block sliding down an inclined plane, a disk rotating within a rigid hoop to assess frictional torque balance, and a grid-refinement study demonstrating convergence to the analytical Hertzian solution for two tangentially shearing disks. We further demonstrate robust simulations of complex contact-rich dynamics involving multiple deformable elastic bodies undergoing simultaneous self-contact and inter-body friction while settling in fluid under gravity or being driven by neighboring solids. These results establish RMT as a practical Eulerian framework for simulating frictional contact in deformable fluid–structure interaction problems.