Initial BiGlobal Stability Analysis of the BOLT II Flight Experiment

Butler, Cameron; McKiernan, Gregory; Wheaton, Bradley M.

doi:10.2514/6.2023-0291

Cited by 5 publications

References 11 publications

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ML for fast assimilation of wall-pressure measurements from hypersonic flow over a cone

Morra,

Meneveau,

Zaki

2024

Sci Rep

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Data assimilation (DA) integrates experimental measurements into computational models to enable high-fidelity predictions of dynamical systems. However, the cost associated with solving this inverse problem, from measurements to the state, can be prohibitive for complex systems such as transitional hypersonic flows. We introduce an accurate and efficient deep-learning approach that alleviates this computational burden, and that enables approximately three orders of magnitude computational acceleration relative to variational techniques. Our method pivots on the deployment of a deep operator network (DeepONet) as an accurate, parsimonious and efficient meta-model of the compressible Navier–Stokes equations. The approach involves two main steps, each addressing specific challenges. Firstly, we reduce the computational load by minimizing the number of costly direct numerical simulations to construct a comprehensive dataset for effective supervised learning. This is achieved by optimally sampling the space of possible solutions. Secondly, we expedite the computation of high-dimensional assimilated solutions by deploying the DeepONet. This entails efficiently navigating the DeepONet’s approximation of the cost landscape using a gradient-free technique. We demonstrate the successful application of this method for data assimilation of wind-tunnel measurements of a Mach 6, transitional, boundary-layer flow over a 7-degree half-angle cone.

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ML for fast assimilation of wall-pressure measurements from hypersonic flow over a cone

Morra,

Meneveau,

Zaki

2024

Sci Rep

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Measurements of Natural Turbulence During the BOLT II Flight Experiment

Wirth,

Bowersox,

Dufrene

et al. 2024

Journal of Spacecraft and Rockets

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A Mach 6.0 flight experiment was performed to characterize the turbulent skin friction and heat flux associated with natural transition for vehicle-length Reynolds numbers up to 45 million. This boundary-layer turbulence flight, termed BOLT II, was the second in a series coordinated by the Air Force Office of Scientific Research. Surface heat flux, skin friction, and pressure fluctuation spectra were acquired to characterize the transition process. The test geometry used concave curvature and swept leading edges to introduce a boundary layer with stationary laminar vortex streaks, competing transition mechanisms, and complex early turbulence. The analyses also showed that the spatial evolution of turbulence varied with respect to the location of the vortex heating streaks. Prominent overshoots were observed in the early turbulence within the streak. Turbulence data was collected for Reynolds numbers [Formula: see text] up to [Formula: see text]. A common [Formula: see text] was identified as the start of equilibrium turbulence for the data presented. Conjugate heat transfer simulations, both laminar and turbulent, agreed well with the experimental data, including the laminar leading edge. The Reynolds analogy ratios based on the curve fits to the data, including compressibility, were generally between 0.9 and 1.0. The observed variations were likely the result of the spatial separation of the sensors and different definitions of Stanton number normalization between flight and theory.

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Flat-BOLT Surrogates for Investigating Second-Mode and Crossflow Instabilities

Wernz

2023

AIAA AVIATION 2023 Forum

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Initial BiGlobal Stability Analysis of the BOLT II Flight Experiment

Cited by 5 publications

References 11 publications

ML for fast assimilation of wall-pressure measurements from hypersonic flow over a cone

ML for fast assimilation of wall-pressure measurements from hypersonic flow over a cone

Measurements of Natural Turbulence During the BOLT II Flight Experiment

Flat-BOLT Surrogates for Investigating Second-Mode and Crossflow Instabilities

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