Optimal linear growth in swept boundary layers

Optimal perturbations for the family of three-dimensional boundary layers d escribed by the Falkner-Skan-Cooke similarity solution are obtained using a variational technique in the temporal framework. The disturbances experien cing the most growth take the form of vortices almost aligned with the exte rnal streamline at inception and evolve into streaks. In subcritical flows these can attain about twice the transient amplification observed in compar ably forced two-dimensional flows. Possible connections between optimal per turbations and exponentially amplified crossflow vortices are explored.