Stereoscopic measurement of free surface flows

Abstract

Abstract. The present paper adresses the problem of combined three-dimensionnal measurements of shape and velocity of moving free surfaces. A measurement method based on the cross-correlation of image pairs obtained from a calibrated stereoscopic vision system is presented. The underlying concept of the method consists in the generation of parametric shape and displacement forms which are directly projected on the camera models. This procedure is then integrated in an iterative optimization process so that elevation, orientation, curvature and displacement of each surface subset are accurately estimated. Application is made on inclined plane flows of complex non-Newtonian fluids as an alternative to conventionnal rheometric devices.

Wave patterns generated by an axisymmetric obstacle in a two-layer flow

“…In the present study, an optical stereoscopic technique is deployed to measure an instantaneous field of the elevation of an interface located between two layer of fluid. Stereoscopic techniques have been widely used to measure surface elevation in free surface flows [4,7,9,10,14]. The technique is based on the determination of the position of different points, in the laboratory frame of reference, via their imaged positions in the image planes of two separate cameras.…”

Combined stereoscopic wave mapping and particle image velocimetry

“…The most effective way is then to use a multi-view system that provides a reconstruction through stereoscopic algorithms [19]. In the case of water, we can mention the work of [4,5] or [6] that resolved the free surface in small scale experiments. The implementation of these techniques requires the presence of a pattern on the free surface in order to identify the correspondence of points in the different views.…”

“…In ref. [4,5], Digital Image Correlation (DIC) was used to optimize a global functional form for the surface shape. This is appropriate for smooth deformations, as obtained in solid mechanics or in the viscous flows occurring in small scale experiments.…”