Simulation of multiple spheres falling in a liquid-filled tube

A new 3D finite element how simulation capability for fluid-particle interactions is presented and applied to study time-dependent behavior of multiple spheres falling in a liquid-filled tube. This capability is based on the flow simulation strategies such as stabilized space-time formulation for moving boundaries and interfaces, automatic mesh generation with structured layers of elements around the spheres, automatic mesh moving with remesh only as needed, and the implementation of these strategies on massively parallel computing platforms. Several cases of multiple spheres falling in a liquid-filled tube are studied, with the number of spheres ranging from two to five. In all cases, depending on the number of spheres and their initial arrangement, a stable state is eventually reached with all spheres arranged in a pattern corresponding to that stable state, and with all of them falling with the same terminal velocity.