Abstract
In this study, pressure distributions were reconstructed from phase-locked surface deformation measurements on a thin plate. Slope changes on the plate surface were induced by an external flow interacting with the specimen and measured with a highly sensitive deflectometry setup. The Virtual Fields Method (VFM) was used to obtain pressure reconstructions from the processed surface slopes and the plate material constitutive mechanical parameters. The applicability of the approach in combination with phase-locked measurements is demonstrated using a synthetic jet setup generating a periodic flow in air. Phase-averaging slope data allows mitigating random noise effects and resolving low-range differential pressure amplitudes despite the turbulent flow. The size of the spatial structures of the investigated low amplitude flow events identified in full-field with the present method are mathcal {O}(1)~text {mm}, which is beyond the capabilities of other available surface pressure measurement techniques. Challenges and limitations in achieving the metrological performance for resolving the observed surface slopes of mathcal {O}(0.1)~text {mm km}^{-1} are described and improvements for future applications are discussed.
Highlights
Full-field surface pressure information is required for the research of flow-structure interactions, the design of aerodynamic components, and applications for heat and mass transfer
Surface deformation measurements on thin plates were used as basis for force and pressure reconstruction
This study presents an approach for full-field pressure reconstructions from phase-locked optical surface slope measurements
Summary
Full-field surface pressure information is required for the research of flow-structure interactions, the design of aerodynamic components, and applications for heat and mass transfer. A number of studies have focused on obtaining pressure information from optical deformation measurements on surfaces instead This was achieved by solving the mechanical equilibrium equations of the investigated specimen. The local equilibrium equation for a thin plate in pure bending, which can be obtained using the Love-Kirchhoff theory, requires fourth-order deflection derivatives to calculate pressure. This leads to an amplification of the experimental noise and increases the need for regularization. In [17, 19], noise amplification was addressed using wave number filters on the deformation data, which was obtained with Laser Doppler Vibrometer (LDV) measurements These were used to solve the equilibrium equation and identify external mechanical vibration
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