Simulating of the admixture spreading in a steady 2D lengthy stream of the viscous fluid

The problem of the passive contaminant spreading in a steady viscous fluid stream is discussed while the
admixture's dissipation and diffusion are taken into account. The channel is assumed to be a horizontal
plane, curvilinear and quite lengthy, so that the ratio of the stream width to its length can be regarded as
a small parameter. A mathematical model of the process derived by the small parameter technique from
the 2D steady Navier-Stokes equations for incompressible viscous fluid and non-steady convection-diffusion
equation of a substance in the moving medium is introduced. A finite element method is applied for
numerical study of the proposed model and results of computer experiments are presented.