Effect of 2D and 3D Imperfections on Laminar-Turbulent Transition

Hybrid laminar flow technology is a promising way to reduce friction drag, and therefore increase range or decrease operating costs and energy consumption. Full laminar wings would result in approximately 10 % reduction of total drag. Sustained efforts in this domain have already brought optimised wing profiles, adequate perforated panels and validated prediction methods and tools. Such techniques were successfully used on flight tests, involving Dassault Falcon and Airbus A320. Analysis of these tests brought forward the necessity of a precise knowledge of the effect of small surface imperfections on the laminar-turbulent transition. New criteria, based on linear stability theory, have been developed for a wide range of configurations, from 2D incompressible to 3D transonic flow.