Non-linear growth and breakdown toward turbulence in Hypersonic Boundary layers: Investigation of fundamental physical mechanisms
Technical Report,15 Aug 2016,14 Aug 2019
TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION COLLEGE STATION United States
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The work performed under this grant addresses two important aspects that affect accurate computation and prediction of transition to turbulence in hypersonic boundary layers i the non-linear breakdown toward turbulence physics is not well understood in hypersonic boundary layers and ii computational methods based directly on gas kinetic theory have not been as well developed, despite their inherent advantages for computing hypersonic flows. Three studies are performed to address the above gaps in the current state of the art. In the first study, critical mathematical framework to analyze and understand the non-linear internal-kinetic energy interactions and subsequent spectral energy transfer is developed. This development is the first of its kind to clearly identify and explain the interchange between the mean and fluctuating fields of internal and kinetic energy. The second study develops and validates a promising gas kinetic scheme GKS for high-speed wall bounded flows. Validation studies are performed in flows ranging from subsonic speeds to convective Mach number of about 6. The scheme and code are validated against benchmark data and linear theory results. The accuracy of the solver for capturing non-linear physics is also well established. The third study examines perturbation growth and non-linear breakdown to transition at various speeds. The contrast between incompressible flow and hypersonic flow non-linear breakdown physics is well established. It is shown that kinetic-internal energy exchange can lead to significant slow down in the transfer of energy from large to small scales. In turn, this can delay the onset of breakdown in high speed flows. Overall, the studies performed under this proposal, lead to valuable advances in our ability to compute and predict the transition phenomenon in hypersonic boundary layers.
- Fluid Mechanics