Numerical modeling of dispersion of non-spherical particles by waves and currents

We numerically investigated the dispersion of non-spherical particles in a wave-current flow, with a focus on determining how various parameters, grouped into nondimensional numbers, impact dispersion. We performed simulations of negatively buoyant ellipsoids falling from the surface of a wave-current flow with varied initial particle orientation and wave phase. We examined the impact of the following nondimensional numbers on particle dispersion, which together fully describe the input parameter space for this system according to the Buckingham Pi theorem: the Archimedes number, the Stokes number, the particle eccentricity, the Keulegan-Carpenter number, the ratio between the Stokes drift and particle settling time scales, and the wave steepness. We found that no single parameter dominated the dispersion, and that no single nondimensional number could fully explain the results; nearly all of them were significant in determining the dispersion. Our results have ramifications for modeling the transport of microplastics near the surface of the ocean.