COMSOL Multiphysics was used in this investigation of Multiphase flow: Solid, neutrally buoyant spherical particles interact with one another in a viscous fluid. Any interaction between the two particles can described by the combination of four unique 'modes':
1. Rotation about the axis perpendicular to the line of centers between particles
2. Translation along the axis perpendicular to the line of centers between particles
3. Rotation about the line of centers between particles
4. Translation along the axis perpendicular to the line of centers between particles

In this investigation, the forces (if particles are translating) and the torques (if particles are rotating) acting on the particles are of interest. The fields that this research can have an impact on are sediment transport, oil recovery, porous media, and more. The four modes of motion mentioned above can be decoupled and solved for independently. For instance, it is possible to simulate all four modes at once using computational software, then decouple the forces and torques to investigate each mode, individually.