Stability and Breakdown Measurements on the AFRL/AFOSR Boundary Layer Turbulence (BOLT II) Flight Geometry
Date
2022-03-28Metadata
Show full item recordAbstract
The Air Force Research Laboratory/Air Force Office of Scientific Research (AFRL/AFOSR) introduced the Boundary Layer Turbulence (BOLT II) flight experiment to advance the understanding and modeling of naturally occurring and strained hypersonic turbulent boundary layers on a concave surface with swept leading edges. In support of the flight experiment, the objective of this dissertation is to identify and document the transition mechanisms and quantify the breakdown to turbulence on a subscale BOLT II model in hypersonic flow. These studies provide insight into the instabilities and breakdown processes, as well as aiding in the interpretation of the flight test results. Experiments were conducted in the Mach 6 Quiet Tunnel (M6QT) and the Actively Controlled Expansion (ACE) tunnel located at the Texas A&M University National Aerothermochemistry and Hypersonics Laboratory. The flow characteristics on several subscale BOLT II models were investigated. IR thermography measurements were made to examine the global surface heating on the surface in both freestream environments. In the ACE facility, turbulent flow in the form of wedges was present on the model. In the M6QT, elevated heating was observed within the laminar streaks on the model at low Reynolds numbers but laminar-to-turbulent transitional heating occurred at high Reynolds numbers. Fast response surface pressure transducers were placed in the region of breakdown to examine spectral content under quiet and conventional flow. Spectral content was observed by the PCB sensors in the frequency range of 100-275 kHz within the laminar-to-turbulent transition region. Kulite sensors located off-centerline measured a frequency band of 30-40 kHz in both freestream environments. Off-body measurements utilizing constant temperature hot-film anemometry were made in the M6QT to investigate the mixed-mode region on the model. Within the voltage fluctuation energy, a frequency band from 50-75 kHz was seen in the hot-film spectra that increased in amplitude further downstream on the model. Results were compared to computations as well as the benefit of them for designing the instrumentation layout for the BOLT II flight test vehicle.
Subject
flight testhypersonics
experiments
computations
simulations
boundary layer
transition
turbulence
Citation
Kostak-Teplicek, Heather Emily (2022). Stability and Breakdown Measurements on the AFRL/AFOSR Boundary Layer Turbulence (BOLT II) Flight Geometry. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197226.