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We present in this paper a novel approach dedicated to the measurement of velocity in fluid experimental flows through image sequences. Unlike most of the methods based on particle image velocimetry (PIV) approaches used in that context, the proposed technique is an extension of “optical-flow” schemes used in the computer vision community, which includes a specific enhancement for fluid mechanics applications. The method we propose enables to provide accurate dense motion fields. It includes an image based integrated version of the continuity equation. This model is associated to a regularization functional, which preserve divergence and vorticity blobs of the motion field. The method was applied on synthetic images and on real experiments carried out to allow a thorough comparison with a state-of-the-art PIV method in conditions of strong local free shear. [ABSTRACT FROM AUTHOR]

The strong interaction between turbulent structures arising from a plane mixing layer impinging on a circular cylinder is studied. This complex flow has been investigated by a set-up called ?dual-plane? PIV that uses two 2D PIV (two-dimensional particle image velocimetry) planes acquired simultaneously. This approach allowed us to apply a 3D-POD (three-dimensional proper orthogonal decomposition) treatment. The first POD modes show the main footprint of the flow configuration, which comprises oblique structures associated with the action of the mixing layer on the near wake. The present study suggests, by analogy, that this phenomenon behaves like the dislocation observed in uniform wake flows. [ABSTRACT FROM AUTHOR]