Contemporary research is focused on boundary layer transition of swept-wing geometries reseulting in crossflows featuring geometrical discontinuities. The flow around such geometries is complex and remains to be fully understood, despite its known significance to the transition process. A turbulent boundary layer results in more friction drag than a laminar boundary layer. A delay of the transition of a boundary layer has the potential to significantly decrease the aerodynamic drag experienced by the wing.

With the goal to improve the aerodynamics of modern swept-wing designs through a novel flow control technique, experimental and numerical investigations are required. The knowledge gained from these endeavors will aid in improving aeronautical transportation vehicles in terms of economic and environmental performance. In this research, I will aid to this goal via an in-depth investigation of the use of Nonlinear Stability Theory for transition prediction and flow control.

Linear Stability Techniques (LST) and the Parabolized Stability Equations (PSE) are by their definition unsuitable for the rapidly varying flows around steps. The Nonlinear Parabolized Stability Equations (NPSE) are subject to that same limitation as a result of derivation assumptions. Despite these limitations, their efficiency is key for rapid transition prediction, flow control and design. In this research the limits of the NPSE in terms of surface irregularities, steps and secondary instabilities are pushed.