ELLIPTIC INSTABILITY IN 2-DIMENSIONAL FLATTENED TAYLOR-GREEN VORTICES

The aim of the present paper is to study three-dimensional elliptic in stability in two-dimensional flattened Taylor-Green vortices, which co nstitutes a model problem for the topics of wake vortex dynamics. Shor twave asymptotics and classical Linear stability theory are developed. Both approaches show that the flow is unstable. In particular, the st ructure of the most amplified growing mode is the same as that obtaine d in unbounded elliptical flows. The limits of the linear regime and t he effects of the nonlinear interactions are characterized by means of a spectral Direct Numerical Simulation (DNS). (C) 1998 American Insti tute of Physics.