Drag reduction by boundary layer laminarization

This paper gives an overview of the investigations currently performed in the framework of laminar flow control studies. The main laminar-turbulent transition mechanisms (boundary layer tripping by roughness elements, leading edge contamination, ''natural'' transition) are first described, together with the available transition prediction methods. The different techniques for laminar flow control are then presented. They are illustrated by examples of free flight experiments conducted in the US and in Europe. The last part of the paper is devoted to a detailed description of flight tests performed on Falcon 50 and Falcon 900 aircraft in order to validate the concepts of natural laminar flow and hybrid laminar flow control.