High-Precision Digital Image Correlation for Investigation of Fluid-Structure Interactions in a Shock Tube

• Published in: Experimental mechanics Vol. 60; no. 8; pp. 1119 - 1133
• Main Authors: Lynch, K. P., Jones, E. M. C., Wagner, J. L.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2020; Springer Nature B.V
• Subjects: Aerodynamic loads; Aerodynamics; Biomedical Engineering and Bioengineering; Characterization and Evaluation of Materials; Control; Correlation analysis; Digital imaging; Dynamical Systems; Engineering; Flash lamps; Fluid dynamics; Fluid flow; Fluid-structure interaction; Image reconstruction; Lasers; Light sources; Noise; Noise reduction; Optical communication; Optical Devices; Optical distortion; Optics; Photonics; Research Paper; Resonant frequencies; Solid Mechanics; Transverse loads; Vibration; Vortex shedding; Xenon; Digital image correlation; Shock tube; Fluid structure interaction
• DOI: 10.1007/s11340-020-00610-8
• ISSN: 0014-4851

Background: Structural response measurements are challenging in aerodynamic testing environments due to high-speed requirements, facility vibrations, and the desire for non-intrusive measurements. Objective: This study uses stereo digital image correlation (DIC) to investigate the response of a jointed beam under aerodynamic loading in a shock tube. Methods: The incident shock subjects the beam to an impulsive frontal load followed by periodic transverse loading from vortex shedding. Several considerations necessary to realize high-precision are addressed: first, a hybrid stereo camera calibration accounted for tangential distortions when imaging through thick windows. Second, a measurement bias from Xenon flash-lamp light sources was identified and removed using laser illumination. Third, facility motion was mitigated by vibration isolation and appropriate signal filtering. Finally, aero-optical distortions from turbulence were removed using a low-order reconstruction. Results: The resulting displacement data has a noise floor of approximately ± 1 μm at 20 kHz sampling rate. The reduction of primary noise sources allows a transient structural response on the order of 10–40 μm to be quantified. The highest vibrations occurred when the vortex shedding frequency matched the beam’s natural frequency. Conclusion: the noise reduction techniques described allow for structural measurements requiring high-precision, non-intrusive displacement data to be performed in aerodynamic environments.