Accurate simulation of transport processes in two-dimensional shear flow

The paper describes a substantial improvement to an existing modelling approach for two-dimensional solute transport. The flow field is represented by a series of streamtubes in which advection is simulated using a highly accurate semi-Lagrangian numerical scheme. Transverse mixing between the streamtubes is treated with a standard numerical method for diffusion. Numerical experiments demonstrate that accurate simulations of the longitudinal dispersion caused by the interaction of a simple transverse velocity profile and transverse diffusion can be obtained over a wide range of time-steps provided that the diffusion occurring during the time-step is properly accounted for. The model is ultimately limited by the relatively poor numerical treatment of transverse diffusion, but this could be remedied by employing an enhanced numerical method for this term. The paper concludes that this is an area in which future modelling efforts need to be directed.