Surface Pressure Reconstruction from Phase Averaged Deflectometry Measurements Using the Virtual Fields Method

Abstract

AbstractIn 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 $\mathcal {O}(1)~\text {mm}$O(1)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 $\mathcal {O}(0.1)~\text {mm km}^{-1}$O(0.1)mm km−1 are described and improvements for future applications are discussed.