Analysis and treatment of errors due to high velocity gradients in particle image velocimetry

Patrice Meunier (1) , Thomas Leweke (1)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre

This paper deals with errors occurring in 2D cross-correlation PIV algorithms (with window shifting), when high velocity gradients are present. A first bias error is due to the difference between the Lagrangian displacement of a particle and the real velocity. This error is calculated theoretically as a function of the velocity gradients, and is shown to reach values up to 1 pixel if only one window is translated. However, it becomes negligible when both windows are shifted in a symmetric way. A second error source is linked to the image pattern deformation, which decreases the height of the correlation peaks. In order to reduce this effect, the windows are deformed according to the velocity gradients in an iterative process. The problem of finding a sufficiently reliable starting point for the iteration is solved by applying a Gaussian filter to the images for the first correlation. Tests of a PIV algorithm based on these techniques are performed, showing their efficiency, and allowing the determination of an optimum time separation between images for a given velocity field.

Domaines: Mécanique des fluides [physics.class-ph]

Patrice Meunier, Thomas Leweke. Analysis and treatment of errors due to high velocity gradients in particle image velocimetry. Experiments in Fluids, 2003, 35 (5), pp.408 - 421. ⟨10.1007/s00348-003-0673-2⟩. ⟨hal-00014834⟩