TY - GEN
T1 - Reconstructing Hypersonic Flow Over a Bluff Body from Experimental Background-Oriented Schlieren Data
AU - Molnar, Joseph P.
AU - Lalonde, Elijah J.
AU - Combs, Christopher S.
AU - Grauer, Samuel J.
N1 - Publisher Copyright:
© 2024 by the authors.
PY - 2024
Y1 - 2024
N2 - Background oriented schlieren (BOS) is a non-intrusive flow visualization technique that is used to characterize density in complex, high-speed flows. Hypersonic flows over bluff bodies are increasingly relevant to the design of next-generation air- and spacecraft, and BOS may help to study these devices. BOS measurements indicate 2D density gradients in the working fluid, which can be leveraged to render shock structures, quantify density ratios, and even reconstruct latent fields like velocity and pressure. High-speed tests require a fast camera exposure to freeze the flow, but increasing the shutter speed limits the signal strength, resulting in a low signal-to-noise ratio (SNR). Opening the aperture allows more light onto the sensor, increasing the SNR, but it also limits the camera’s depth of field and leads to blurry deflections. To address this, we develop an accurate forward model of BOS imaging that accounts for depth-of-field effects. We employ this model to reconstruct the density field of a hypersonic flow over a spherical bluff body. The flow is well characterized in the literature and thus provides a suitable benchmark for our algorithm. Reconstructions are performed using the neural-implicit reconstruction technique, and we also report “physics-informed” estimates based on the compressible Euler equations. Our aperture sampling approach dramatically improves the accuracy of reconstructions: the sharp shock interface is well-resolved in all our tests, irrespective of the camera’s aperture setting.
AB - Background oriented schlieren (BOS) is a non-intrusive flow visualization technique that is used to characterize density in complex, high-speed flows. Hypersonic flows over bluff bodies are increasingly relevant to the design of next-generation air- and spacecraft, and BOS may help to study these devices. BOS measurements indicate 2D density gradients in the working fluid, which can be leveraged to render shock structures, quantify density ratios, and even reconstruct latent fields like velocity and pressure. High-speed tests require a fast camera exposure to freeze the flow, but increasing the shutter speed limits the signal strength, resulting in a low signal-to-noise ratio (SNR). Opening the aperture allows more light onto the sensor, increasing the SNR, but it also limits the camera’s depth of field and leads to blurry deflections. To address this, we develop an accurate forward model of BOS imaging that accounts for depth-of-field effects. We employ this model to reconstruct the density field of a hypersonic flow over a spherical bluff body. The flow is well characterized in the literature and thus provides a suitable benchmark for our algorithm. Reconstructions are performed using the neural-implicit reconstruction technique, and we also report “physics-informed” estimates based on the compressible Euler equations. Our aperture sampling approach dramatically improves the accuracy of reconstructions: the sharp shock interface is well-resolved in all our tests, irrespective of the camera’s aperture setting.
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U2 - 10.2514/6.2024-2493
DO - 10.2514/6.2024-2493
M3 - Conference contribution
AN - SCOPUS:85187397375
SN - 9781624107115
T3 - AIAA SciTech Forum and Exposition, 2024
BT - AIAA SciTech Forum and Exposition, 2024
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
T2 - AIAA SciTech Forum and Exposition, 2024
Y2 - 8 January 2024 through 12 January 2024
ER -