High Magnification Telecentric Background Oriented Schlieren (BOS) and its Application to a Supersonic Turbulent Boundary Layer

Zhou, Terry; Gaskins, Jonathan; Swaine, Suzanne; Bane, Sally P.; Poggie, Jonathan; Blaisdell, Gregory A.

doi:10.2514/6.2023-2437

Cited by 4 publications

(1 citation statement)

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“…Application of this exact telecentric BOS system to a Mach 2 turbulent boundary layer demonstrated improved spatial resolution (172 µm) of wallnormal density gradient profile measurements. The acquired density gradient profile also showed excellent agreement with high-fidelity computational results Zhou et al (2023Zhou et al ( , 2024.…”

Section: Bos Measurementssupporting

confidence: 81%

Comparison of Displacement Estimation Techniques for Background Oriented Schlieren of High-speed Compressible Turbulent Flows

Zhou,

Gaskins,

Poggie

et al. 2024

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Background oriented schlieren (BOS) is a non-intrusive optical method for measuring density gradients in a fluid flow based on changes of local refractive index.The density gradients can be obtained by observing the displacement betweentwo images of a background pattern, with and without the presence of the flow.Existing methods to estimate displacements include block matching and optical flow. Image registration in computer vision seeks reasonable transformationsbetween two images such that one matches the other and has been under-utilizedin determining the displacement for BOS image processing. Deformable imageregistration (DIR) methods allow non-global transformations and are proposedas displacement estimation methods for processing BOS images. Numerical raytracing simulations are performed to generate synthetic BOS images of variousflows. The estimated density gradient results of block matching, optical flow,and DIR methods are compared to the ground truth (the path-averaged densitygradient of the schlieren object used in ray tracing) to assess and compare theirperformances. The performances of these methods are also validated on experimental BOS images to determine the displacement estimation method that ismost suitable for high-speed, turbulent flows.

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Section: Bos Measurementssupporting

confidence: 81%