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
Partner: Aerion Corporation
designed and built the flight test article, and Armstrong provided
the ground and flight support.
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.