The free jets as boundary-layer flows induced by continuous stretching surfaces

This paper proves that the free laminar jets of the classical hydrodynamics may be identified with certain boundary-layer flows induced by continuous surfaces immersed in quiescent incompressible fluids and stretched with wel l-defined velocities. In this sense: (i) Schlichting's round jet of momentu m flow J over dot coincides with the axisymmetric flow induced by a thin co ntinuous wire issuing from a small orifice at x = 0 and stretching along th e x-axis with velocity U-w(x) = 3J over dot/(8 pi rho nux), and (ii) the Sc hlichting-Bickley plane jet of momentum flow i coincides with the boundary- layer flow induced by an impermeable plane wall issuing from a long slit (o f length l) and stretching with velocity U-w(x) = [3J over dot(2)/(32 nu rh o (2)l(2)x)](1/3).