Numerical Simulation of the Wave-Induced Drift of Floating Marine Plastic Debris Modeled as Discrete Particles

The Ocean Cleanup Foundation is developing floating barrier systems to concentrate and extract buoyant plastics from the global accumulation regions located in the subtropical convergence zones in the world’s oceans. In this context, it is important to understand the transport and accumulation of these floating marine debris. Since marine litter transport is a multiscale problem, it is important to know the transport of these objects at their very own scale. For this end, two Discrete Particle Models have been implemented in the open-source two-phase Navier-Stokes flow solver Basilisk to study their wave-induced drift: i) using a simple linear interpolation and ii) using the high-order WENO interpolation scheme (Jiang and Wu [1999]) combined with reference frame intrinsic to the particle and its time-dependent submergence. It is shown that in longtime trajectory along the free surface, the two models differ drastically and the sophisticated one shows the best performance. A performance that is highlighted through a wave-induced drift factor defined as the ratio between the wavelength averaged plastic velocity and the wavelength averaged water particle Stokes drift.