LOCALIZED ASYMPTOTIC SOLUTIONS OF THE NAVIER-STOKES EQUATIONS AND LAMINAR WAKES IN AN INCOMPRESSIBLE FLUID

Equations are derived to describe the far-field laminar wake behind a body in incompressible fluid flow with an arbitrary distribution of th e free-stream (unperturbed flow) velocity. For certain classes of free -stream flows, analysis of these equations enables various processes i n narrow wakes or jets to be described (the interaction of the longitu dinal transverse velocity components in a jet, cause it to accelerate or decelerate and conservation of the energy of the wake by distortion of its trajectory regardless of viscous dissipation). In particular, conditions are obtained for the wake growth in spiral flows, analogous to the Rayleigh conditions for the instability of radially symmetric flows relative to three-dimensional short-wave perturbations. (C) 1998 Elsevier Science Ltd. All rights reserved.