Some properties of the three-dimensional boundary layer equations

The analysis deals with a system of Schlichting-type three-dimensional boundary layer equations for no-slip or suction conditions at the surface of the body. It is shown that in the case of negative longitudinal and transverse components of the pressure gradient and the corresponding boundary conditions, the longitudinal and transverse components of the velocity vector are positive not only at the body but also over the boundary layer thickness. This makes it possible to obtain upper bound estimates of the velocity components as a function of the boundary conditions and to determine the behavior of the line-of-flow projections onto the surface of the body.