A conservativemulti-tracer transport algorithmon the cubed-sphere based on the semi-Lagrangian approach (CSLAM) has been developed. The scheme relies on backward trajectories and the resulting upstream cells (polygons) are approximated with great-circle arcs. Biquadratic polynomial functions are used for approximating the density distribution in the cubed-sphere grid cells. The upstream surface...

We study the submonolayer diffusion of hard disks and rodlike molecules on smooth surfaces through numerical simulations and theoretical arguments. We concentrate on the behavior of the various diffusion coefficients as a function of the two-dimensional (2D) number density rho in the case where there are no explicit surface-particle interactions. For the hard disk case, we find that while the t...

In this presentation we overview some recent results on biased tracer diffusion in lattice gases. We consider both models in which the gas particles density is explicitly conserved and situations in which the lattice gas particles undergo continuous exchanges with a reservoir, which case is appropriate, e.g., to adsorbed monolayers in contact with the vapor phase. For all these models we determ...

We study gravity-driven suspension currents sustained by continuous sediment erosion at the head. In this regime, basal erosion behaves as a narrow, steady supply of higher-density fluid into the current’s front. We suggest a possible bed induced erosion mechanism which delivers particles to the front. We investigate the head of such erosive suspension currents with laboratory experiments, theo...

The average concentration of tracers advected from a point source by a multivariate normal velocity field is shown to deviate from a Gaussian profile. The flatness ~kurtosis! is calculated using an asymptotic series expansion valid for velocity fields with short correlation times or weak space dependence. An explicit formula for the excess flatness at first order demonstrates maximum deviation ...

We present a new method for a two-dimensional linear advection-diffusion problem of a “tracer” within an ambient fluid. The problem should have isolated external sources and sinks, and the bulk fluid flow is assumed to be governed by an elliptic problem approximated by a standard locally conservative scheme. The new method, the fully conservative Eulerian-Lagrangian streamtube method, combines ...