Global linear instabilities in laminar separated boundary layer flow

Solutions of the partial derivative eigenvalue problem governing three-dimensional (global) linear instability in incompressible steady laminar boundary-layer flow which encompasses a recirculation bubble have been obtained. Both stationary and pairs of travelling linear instabilities have been discovered, which are distinct from known solutions of the Orr-Sommerfeld equation (OSE) or the linear parabolised stability equations (PSE) instability theories, and can both become unstable. One implication is that current laminar how control approaches based on frequency information delivered by either the OSE or the PSE are incomplete as far as travelling disturbances are concerned and inadequate for control of unstable global stationary how eigenmodes.