A HYDRODYNAMIC PARTICLE TRACKING ALGORITHM FOR SIMULATING SETTLING OFSEDIMENT

The transport of sediment is an aggregated phenomenon reflecting the r esponse of individual sediment particles to the surrounding fluid flow . Traditional modelling of sediment transport has concentrated on conc eptualisations of either the overall behaviour (analogous to the therm odynamic approach to atomic modelling) or simplifications of the movem ent of individual particles that assume that the motion of a particle is the same as that of the surrounding fluid (analogous to a simplific ation of the particle dynamics approach to atomic modelling). This pap er describes a numerical technique that models the hydrodynamics of in dividual sediment particles in a turbulent flow field, tracking the pa th of the particle under the action of a mean velocity field and super imposed random fluctuations, thus inferring data about the aggregate t ransport. The movement of individual sediment particles is modelled by analysing the drag forces acting on a particle under the action of a turbulent flow field and calculating its motion from a force balance. Particles never move with exactly the same motion as the surrounding f luid, they lag behind it generating the drag force that drives the par ticle's motion. In an example, it is shown that turbulence has a signi ficant effect on settling velocity of particles compared with the stil l water case. Settling velocities increase or decrease depending on th e turbulence applied.