Summary:
The current research at the Supersonic Wind Tunnel is in developing a robust technique to minimize the strength of the sonic boom for supersonic aircraft. This research, called the Quiet Supersonic Platform (QSP) will benefit from the earlier work completed at the Unsteady Wind Tunnel concerning laminar flow control (LFC) for the crossflow instability inherent in the flow over a swept wing. By maintaining laminar flow over a majority of the wing surface, drag will be drastically reduced. This results in increased fuel efficiency and, thus, a large drop in the weight of the aircraft. Some of the techniques that will be utilized to study the instability are briefly discussed below.
Development Objectives:
The development objective of the QSP is to perform a technology demonstration and validation of swept-wing laminar flow control at Mach 2.4. A laminar wing would result in fuel savings due to decreased drag, and the attendant weight reduction would reduce the sonic-boom strength.
Technical Challenges:
The principle control problem concerns crossflow instability, which has been thought to be controlled only by boundary-suction. Recent low-speed experiments at Arizona State University show that distributed roughness near the attachment line can maintain a laminar boundary layer. Therefore, the research must determine, demonstrate and validate critical induced roughness wavelengths and methods of introduction for supersonic flow. The goal is to attain 80% laminar flow on the upper and lower surfaces.
Technical Approach:
The end product will be a swept LFC airfoil with natural laminar flow on the upper surface. It will also delay transition on the lower surface with micron-size roughness at specific wavelengths near the leading edge. To accomplish this, validated experiments and computations will be performed using: the Supersonic Wind Tunnel, NPSE prediction codes, and F-15B flight tests at NASA-Dryden. It will produce supersonic LFC technique and design tools, and a robust laminar flow detector system for flight.
