Modelling sheetflow sediment transport in wavebottom boundary layers using discreteelement modelling

Sediment transport in oscillatory boundary layers is a process that drives coastal geomorphological change. Most formulae for bedload transport in nearshore regions subsume the smallestscale physics of the phenomena by parametrizing interactions amongst particles. In contrast, we directly simulate granular physics in the wavebottom boundary layer using a discreteelement model comprised of a threedimensional particle phase coupled to a onedimensional fluid phase via Newton's third law through forces of buoyancy, drag and added mass. The particulate sediment phase is modelled using discrete particles formed to approximate natural grains by overlapping two spheres. Both the size of each sphere and the degree of overlap can be varied for these composite particles to generate a range of nonspherical grains. Simulations of particles having a range of shapes showed that the critical anglethe angle at which a grain pile will fail when tilted slowly from restincreases from approximately 26 for spherical particles ...