Laminar Flow Flight Experiments — A Review

On December 17, 1937, B. Melvill Jones presented the first Wright Brothers’ lecture at Columbia University in New York (Ref. 1). His lecture, which was entitled “Flight Experiments on the Boundary Layer,” dealt specifically with the first British flight observations of transition of the boundary layer from laminar to turbulent flow. These data, Jones concluded, showed that it is possible to retain a laminar layer over at least one-third of the whole wing surface even when the chord Reynolds number is as high as 8 millions. In the 50 years since this presentation, much flight research has been performed to explore the potential of laminar flow control for drag reduction. Both passive control and active control by suction (designated as natural laminar flow and laminar flow control, respectively) have been researched and impressive results achieved. The successes of the early natural laminar flow (NLF) flight testing were remarkable, with the achievement of an extent of laminar flow and transition Reynolds numbers which were not to be exceeded in flight for over 40 years. Nevertheless, mid-century manufacturing capabilities were such that insufficiently smooth or wave-free wing surfaces led to failure of attempts to transfer this technology to practice. The experience with laminar. flow control (LFC) nearly paralleled that of NLF.