LINEAR MECHANISM OF WAVE EMERGENCE FROM VORTICES IN SMOOTH SHEAR FLOWS

A new linear mechanism of wave abrupt emergence from vortices in smoot h shear flows is found. The phenomenon is closely related to non-norma lity of linear dynamics of disturbances in shear flows and is best int erpreted in the framework of a nonmodal approach-by tracing of linear dynamics of spatial Fourier harmonics of vortex in time. Found phenome non, demonstrated in the Letter for the simplest example of unbounded, compressible, plane Couette flow, should be important for numerous en gineering applications and should be realized in various terrestrial a nd astrophysical shear flows. [S0031-9007(97)04399-8].