Diffusion and advection in two-dimensional rotating flow

This paper presents the results of an investigation of mass transport by diffusion and advection in two-dimensional steady, spatially varied confined flow. In practice, this type of flow occurs in recirculating regions ofstreams and rivers or behind hydraulic structures. A simple vorticity transport model is used to simulate shear-induced flow in a square region confined on three sides and open to a uniform flow on one side. The differential equation governing diffusion and advection of a known quantity of tracer mass introduced in such flow is solved. The solution scheme is based on Galerkin finite element approximation of the transport equation. Diffusion is represented by a second-order tensor, the components of which are related to the eddy diffusion coefficient, as well as the magnitude and direction of the mean local velocity. The unsteady transport term is approximated by implicit finite differencing in time. Simulation results are given for one and two-dimensional test cases and for shear induced rotating flow.U.S. Department of the InteriorU.S. Geological SurveyOpe