A two-phase approach to wave-induced sediment transport under sheet flow conditions

Abstract

A numerical model for the general description of the sediment transport under oscillatory sheet flow conditions is developed based on a two-fluid representation of the two-phase turbulent flows. The governing equations of the model are the Reynolds averaged continuity equations and equations of motion for both the fluid and the sediment phases. The two phases are coupled by the interphase forces including the resistance force, the inertia force, and the lift force. Turbulence closure of the fluid phase is based on a slightly modified k– ε model while an algebraic particle-turbulence model is applied to the sediment phase. The numerical method is based on the modified SIMPLE scheme and an improved time stepping technique. The model is validated by the published data for the symmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at the University of Tokyo and for both the symmetrical and the asymmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at University of Aberdeen. The numerical results on the temporal and spacial variation of the sediment concentration, the horizontal velocities of the two phases, the horizontal and vertical fluxes of the sediment phase, as well as the thickness of the sheet flow layer all show satisfactory agreement with the laboratory data. The model is also shown to predict the net sediment transport rate with a reasonably good accuracy.