Abstract:
This study presents an exact solution to the Navier–Stokes equations for a steady non‑uniform Poiseuille shear flow in an infinite horizontal fluid layer. For this class of flows, the governing system reduces to a nonlinear overdetermined set of partial differential equations. A nontrivial exact solution is constructed within the Lin–Sidorov–Aristov class, wherein the velocity field is given by linear forms of two horizontal coordinates with coefficients depending on the vertical coordinate. The boundary‑value problem employs the Navier slip condition at the lower wall and a non‑uniform velocity profile at the upper boundary. The resulting polynomial solution is analyzed, revealing that counter‑flows can emerge due to the presence of stagnation points. It is shown that the Navier condition can lead to a maximum stratification of the velocity field into four distinct zones (three stagnation points). In the limiting case of perfect slip, the analysis demonstrates the possibility of two stagnation points.