INVISCID SECONDARY INSTABILITY OF THE FAR WAKE

The three-dimensional (3-D) instability of a parallel mean flow and a two-dimensional (2-D) wave is examined. Such secondary instability is shown to exist for the Gaussian profile as a model for the wake. Numerical results are obtained based upon a recently proposed wave-mean-flow interaction mechanism, with the assumptions of temporal problem and inviscid flows. Classical 2-D instability is strong in the near wake but decays to zero in the far wake, where it is overwhelmed by 3-D instability. It is conjectured that this will qualitatively explain the emergence of three-dimensionality in the far wake. © 1990 American Institute of Physics.