A modified loose-coupling approach for nonspherical particle-particle collisions within a fluid

Nonspherical particle-particle interactions within a fluid are numerically studied using the sharp-interface curvilinear immersed boundary (CurvIB) method coupled to kinematic equations of motion. Detecting collisions between non-spherical particles is not as straightforward as spherical ones, for which a search accelerated with control cell and bounding box strategies is implemented. To model the behavior after a collision, the coefficient of restitution and conservation of momentum equations are used. For verification, energy conservation of the particles for fully elastic collisions (coefficient of restitution of one) is demonstrated. The collision is modeled as instantaneous, i.e., the collision time is negligible and is not dependent on time, unlike the soft-sphere approach. For this reason, numerical instability will occur in simulations of particle-particle collisions in fluids. To overcome this, a modified loose-coupling approach is developed and tested.