Estimation et analyse de champs denses de vitesses d'écoulements fluides

Thomas Corpetti 1
1 VISTA - Vision spatio-temporelle et active
IRISA - Institut de Recherche en Informatique et Systèmes Aléatoires, Inria Rennes – Bretagne Atlantique
Abstract : This thesis is concerned with fluid motion analysis in image sequences and involves two main issues. In a first part, we address the problem of estimating a dense motion field. Due to the great deal of spatial and temporal distortions that luminance patterns exhibit in fluid imagery, standard techniques from Computer Vision, originally designed for quasi-rigid motions with stable salient features, are not well adapted. In that prospect, we investigate a dedicated energy-based motion estimator. The considered functional includes an original data model relying on the continuity equation of fluid mechanics. This new data model, which is specifically designed to be embedded in a multiresolution framework, is associated to an original ``div-curl'' type regularization. The performances of the resulting fluid flow estimator are demonstrated both on synthetic and real meteorological image sequences. The method is furthermore validated on an experimental flow representing a free turbulent shear layer. The second step of this study is concerned with the analysis of a dense motion field preliminary estimated between two images of a fluid video. We propose a method to extract the vortices and sources/sinks following the Rankine model. This problem is for instance essential in meteorology (to identify and track depressions or convective clouds in satellite images) or to characterize experimental fluid flows. The knowledge of such structures allows in addition a compact representation of the flow which is very useful in both experimental and theoretical fluid mechanics. The method we propose here is based on an analytic representation of the flow and has the advantage to extract others pertinent informations of the motion (such as potential functions, the Helmholtz decomposition, singular points, ...). This approach is experiment on various displacements fields showing different physicals events.
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Thomas Corpetti. Estimation et analyse de champs denses de vitesses d'écoulements fluides. Interface homme-machine [cs.HC]. Université Rennes 1, 2002. Français. ⟨tel-00005351⟩

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