Abstract
This work presents a methodology for reconstructing full-field surface pressure information from deflectometry measurements on a thin plate using the Virtual Fields Method (VFM). Low-amplitude mean pressure distributions of the order of few mathcal {O}(100) text {Pa} from an impinging air jet are investigated. These are commonly measured point-wise using arrays of pressure transducers, which require drilling holes into the specimen. In contrast, the approach presented here allows obtaining a large number of data points on the investigated specimen without impact on surface properties and flow. Deflectometry provides full-field deformation data on the specimen surface with remarkably high sensitivity. The VFM allows extracting information from the full-field data using the principle of virtual work. A finite element model is employed in combination with artificial grid deformation to assess the uncertainty of the pressure reconstructions. Both experimental and model data are presented and compared to show capabilities and restrictions of this method.
Highlights
Full-field surface pressure measurements are highly relevant for engineering applications like material testing, component design in aerodynamics and the use of impinging jets for cooling, de-icing and drying
Since deflectometry measurements yield surface slopes, the combination with the Virtual Fields Method (VFM) reduces the required order of derivatives of experimental data for pressure reconstruction to one
Slope maps obtained from deflectometry measurements were processed and temporally averaged as described in “Data Acquisition and Processing”
Summary
Full-field surface pressure measurements are highly relevant for engineering applications like material testing, component design in aerodynamics and the use of impinging jets for cooling, de-icing and drying. Another approach is the reconstruction of pressure information from full-field surface deformation measurements by solving the local equilibrium equations. The latter used a VFM approach based on piecewise virtual fields, which allows more accurate descriptions of boundary conditions for complex shapes and heterogeneous materials [20] This approach was extended to random spatial wall pressure excitations in [21], reconstructing power spectral density functions from measured data and using the VFM to describe the plate response. Since deflectometry measurements yield surface slopes, the combination with the VFM reduces the required order of derivatives of experimental data for pressure reconstruction to one. One challenge in varying the window size is that the systematic error varies with it, as well as the effect of random noise on pressure reconstruction This problem is investigated numerically in “Simulated Experiments”.
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