Discrete particle model for sheet flow sediment transport in the nearshore

Abstract

Abstract. Fully three-dimensional discrete particle computer simulations of highconcentration sheet flow transport in oscillatory flows quantify the effect of fluid acceleration on bed load transport in highly unsteady flows typical of nearshore marine environments. A simple impulse-momentum approach explains simulation results and forms the basis for adding an acceleration-related term to widely used energetics sediment transport formulae. Transport predicted by the acceleration term becomes increasingly significant as wave shape approaches the sawtooth profile characteristic of surf zone bores. Simulations integrate F=ma and a corresponding set of equations for the torques for each sphere. Normal and tangential forces between contacting particles are linear functions of the distance between sphere centers and the relative tangential displacement at the contact point, respectively; particle interactions are both inelastic and frictional. Pressure gradient forces generated by the passage of surface gravity waves drive fluid and particle motion in a stack of thin horizontal fluid layers that exchange momentum and exert fluid drag, added mass, and buoyancy forces on particles. Transport properties of the simulated granular-fluid assemblage are robust to large variations in material properties of the particles. Simulated transport rates agree with available experimental data for unsteady transport of coarse sands; the mode of bed load motion, dispersion of bed load particles, and particle segregation by size and density are qualitatively consistent with available particle-scale observations of bed load transport of natural particles.

A semianalytical model for sheet flow layer thickness with application to the swash zone

“…A main outcome was the development of empirical formulas for the net sheet flow sediment transport aimed toward use in large-scale morphodynamic models [Drake and Calantoni, 2001;Hoefel and Elgar, 2003;Watanabe and Sato, 2004;Camenen and Larson, 2006;da Silva et al, 2006;Nielsen, 2006;Gonzalez-Rodriguez and Madsen, 2007;van der A et al, 2010. Formulas for other parameters such as the maximum sheet flow layer thickness, d s , and the maximum erosion depth, d e , were also proposed.…”

Coupling of Boussinesq and sediment transport model in a wave flume

“…Bagnold 10) suggested that ε B should be less than one. However, Drake 11) found this value exceeds one. Van der Molen 12) replaced c f with a friction factor for combined currents and wave.…”

Study of sedimentation of non-cohesive particles via CFD–DEM simulations

“…In this paper, the deposition of two different particle-fluid system is simulated, therefore, the influence of the particle properties on the solid concentration of the sediment bed max can be investigated. Among the particle parameters, the stiffness constant and the damping constant have negligible effect on max in our simulations and the previous researches [31,41], however, the friction coefficient and the initial solid concentration of suspension do influence the max , so this section discusses their effect on max respectively.…”