DISTRIBUTION OF SUSPENDED SEDIMENT OVER WAVE-GENERATED RIPPLES

Oscillatory flow over wave ripples is described by use of a discrete vortex model using the ''cloud in cell'' concept. The distribution of suspended sediment over the ripple bed is simulated by a Lagrangian model, following the track of individual sediment particles. A boundary-layer model is used to determine the strength and the motion of the vortices very close to the ripple, surface. The development of the boundary layer is described by the integrated momentum equation, assuming the boundary layer to be turbulent with a logarithmic velocity profile. In the boundary layer, turbulent diffusion is used to describe the distribution of suspended sediment. Outside the boundary layer along the ripple surface, advection with the velocity field resolved by the discrete vortex model determines the suspended-sediment distribution. The simulated sediment concentrations are compared to measurements from the literature. The agreement between the time averaged simulated concentration profiles and the measurements from an oscillating water tunnel is satisfactory.