Comparison of sonic boom propagation models with measurements above the Earth’s turbulent boundary layer

Abstract

NASA conducted the Sonic Booms in Atmospheric Turbulence (SonicBAT) overflight campaign at Armstrong Flight Research Center in 2016 and Kennedy Space Center in 2017. The sonic booms were generated by F-18 aircraft flying at nearly constant altitudes and at nearly constant, supersonic speeds. Although the primary objective of the campaign was to investigate the effects of turbulence on the propagation of sonic booms from the aircraft, a subset of the SonicBAT datasets can be used to validate sonic boom propagation models. This dataset is obtained from the recording using a microphone mounted at a wingtip of a TG-14 glider flying above the Earth's turbulent boundary layer. With this dataset, effects due to turbulence and ground impedance, which are still poorly understood, are effectively eliminated. Consequently, comparison is made between measurements and models which only account for the nonlinear and absorption effects. Such models are obtained using NASA's PCBoom sonic boom propagation code, which has recently been updated to incorporate the full wind effects and improve the code's accuracy and efficiency. Additionally, near-field signatures of the aircraft using PCBoom’s near-field approximant are also compared with those generated by The Boeing Company using computational fluid dynamics.