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Supersonic Boundary Layer Transition II
Armstrong is continuing a partnership with Aerion Corporation to collect flight data about the extent and stability of natural laminar flow (NLF) at supersonic speeds. SBLT II consisted of flying a natural laminar flow test article beneath NASA's F-15B research aircraft. The objective is to better understand how factors such as Reynolds number and surface roughness affect boundary layer transition from laminar to turbulent at supersonic speeds. Experiment results can be used to help determine the sensitivity of the boundary layer to surface roughness, which can translate into manufacturing tolerances for supersonic NLF wing designs.
Work to date: SBLT II collected boundary layer transition data for the NLF test article at flight numbers up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. Transition data also were obtained for surface roughness elements (trip dots, two-dimensional steps) meant to replicate disturbances intrinsic to the manufacture and operation of a supersonic business jet airplane.
Looking ahead: Additional instrumentation will be added to the NLF test article for a second series of flights. The instrumentation will allow engineers to obtain additional information, such as the pressure distribution over the NLF test article.
Partner: Aerion Corporation designed and built the flight test article, and Armstrong provided the ground and flight support.
Advances scientific research: Investigates the robustness of NLF at supersonic speeds over a special test airfoil
Supersonic Flight Research
Supersonic flight over land is currently severely restricted because sonic booms created by shock waves disturb people on the ground and can damage private property. Since the maximum loudness of a sonic boom is not specifically defined by the current Federal Aviation Administration (FAA) regulation, innovators at NASA have been researching ways to identify a loudness level that is acceptable to both the FAA and the public and to reduce the noise created by supersonic aircraft. Using cutting-edge testing that builds on previous supersonic research, NASA is exploring low-boom aircraft designs and other strategies that show promise for reducing sonic boom levels.
A variety of factors, from the shape and position of aircraft components to the propulsion system's characteristics, determine the make-up of a supersonic aircraft's sonic boom.
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