On dealing with multiple correlation peaks in PIV

A novel algorithm to analyse PIV images in the presence of strong in-plane displacement gradients and reduce sub-grid filtering is proposed in this paper. Interrogation windows subjected to strong in-plane displacement gradients often produce correlation maps presenting multiple peaks. Standard mult...

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Bibliographic Details
Published in:Experiments in fluids 2018-05, Vol.59 (5), p.1-15, Article 89
Main Authors: Masullo, A., Theunissen, R.
Format: Article
Language:English
Subjects:
Algorithms
Boundary layer
Displacement
Engineering
Engineering Fluid Dynamics
Engineering Thermodynamics
Filtration
Fluid- and Aerodynamics
Heat and Mass Transfer
Interrogation
Interrogation window
Research Article
Signal to noise ratio
Velocity gradient
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Summary:A novel algorithm to analyse PIV images in the presence of strong in-plane displacement gradients and reduce sub-grid filtering is proposed in this paper. Interrogation windows subjected to strong in-plane displacement gradients often produce correlation maps presenting multiple peaks. Standard multi-grid procedures discard such ambiguous correlation windows using a signal to noise (SNR) filter. The proposed algorithm improves the standard multi-grid algorithm allowing the detection of splintered peaks in a correlation map through an automatic threshold, producing multiple displacement vectors for each correlation area. Vector locations are chosen by translating images according to the peak displacements and by selecting the areas with the strongest match. The method is assessed on synthetic images of a boundary layer of varying intensity and a sinusoidal displacement field of changing wavelength. An experimental case of a flow exhibiting strong velocity gradients is also provided to show the improvements brought by this technique.
ISSN:0723-4864
1432-1114
DOI:10.1007/s00348-018-2542-z