Inhomogeneous Couette flows for a two-layer fluid

The paper presents a new exact solution to the Navier-Stokes equations which describes a steady shearing isothermal flow of an incompressible two-layer fluid stratified in terms of density and/or viscosity, the vertical velocity of the fluid being zero. This exact solution belongs to the class of functions linear in terms of spatial coordinates, and it is an extension of the classical Couette flow in an extended horizontal layer to the case of non one-dimensional non-uniform flows. The solution constructed for each layer is studied for the ability to describe the appearance of stagnation points in the velocity field and the generation of counterflows. It has been found that the flow of a two-layer fluid is stratified into two zones where the fluid flows in counter directions. It is also shown that the tangential stress tensor components can change their sign.