Supersonic Laminar Flow Control

This technique injects precisely defined stationary transient growth disturbances into the free air slipstream over a wing that develop into streamwise elongated "streaks." These streaks are created with an alternating pattern of low and high streamwise velocity in the boundary layer flow adjacent to the aerodynamic surface of interest. Judicious selection of streak wavelength, amplitude, and profile allows the first-mode instability waves responsible for transition via oblique mode breakdown to be damped while the remaining, uncontrolled waves are kept below an amplification threshold. A similar control concept is also applicable to second mode transition at hypersonic Mach numbers. NASA's Langley Research Center has developed a technology that is projected to extend the laminar flow area over supersonic flight configurations by delaying the transition of boundary layer flow from laminar to turbulent state. This controls laminar flow over airframe components including wings, empennage, engine nacelles, and the nose region of an aircraft fuselage. It can be used in combination with many of the existing techniques for passive and active laminar flow control, but is particularly well-suited for a supersonic natural laminar flow design by virtue of avoiding the space, weight, system complexity, and maintenance penalties associated with suction based laminar flow control.