Kostak, Heather Emily (2020-03). Ground Test Analyses of the AFOSR Boundary Layer Transition (BOLT) Flight Geometry. Master's Thesis. Thesis uri icon

abstract

  • The Air Force Office of Scientific Research Boundary Layer Transition (BOLT) flight experiment is a collaboration between academia, government, and industry. The objective was to challenge the hypersonic aerodynamics community to predict transition in flight for a complex geometry. Quantifying the transition mechanisms on the BOLT geometry is the topic for this thesis. Experiments were performed in a range of ground test facilities, including the TAMU ACE and Mach 6 Quiet tunnels, the Purdue BAM6QT, the NASA 20-inch Mach 6 Air Tunnel, and the CUBRC LENS II facility. The measurements included surface temperature and heat flux maps, high-frequency surface pressure fluctuations, and mass flux contours. The results were compared across the facilities and with quiet direct numerical simulation (QDNS) results from the University of Minnesota. The surface heating under quiet conditions was characterized by a streak structure, and the results were found to agree to within 10% across both quiet tunnels and with the QDNS. Transition was not observed under quiet conditions. However, the boundary layer spectral content indicated instability growth (20-40 kHz) in a primary streak just off of the centerline. Conversely, transition was observed in all of the conventional noise facilities. The modal growth was similar across all facilities, regardless of the freestream environment. The instability within the primary streak roll-up was examined in more detail in the TAMU M6QT using hot-wire anemometry. The surface pressure spectra and 2-D contours showed similar modal growth. The flow structure and instability locations were in qualitative agreement with the simulation results.

publication date

  • May 2020
  • March 2020
  • May 2020
  • May 2020
  • May 2020
  • May 2020