Instability and unsteadiness of aircraft wake vortices

Abstract

This paper presents a review of theoretical and experimental results on stability and other unsteady properties of aircraft wakes. The basic mechanisms responsible for the propagation and the amplification of perturbation along vortices, namly the Kelvin waves and the cooperative instabilities, are first detailed. These two generic unsteady mechanisms are described by considering asymptotic linear stability analysis of model flows such as vortex filaments or Lamb-Oseen vortices. Extension of the linear anallysis to more representative flows, using a biglobal stability approach, is also descrbed. Experimental results obtained using LDV, hot wire and PIV in wind tunneles are presented and they are commented upon the light of theory.