Free surface measurement by stereo-refraction

Gomit, Guillaume; Chatellier, Ludovic; Calluaud, Damien; Lee, David

doi:10.1007/s00348-013-1540-4

Cited by 61 publications

(41 citation statements)

References 18 publications

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“…This method is based on the theory of light refraction and on the analysis of the apparent displacement between a reference and refracted images of a laser sheet through the surface [1]. From this apparent displacement, previous methods used the Snell-Decartes law and strong hypothesis on the geometry of the rays issued from the camera to compute the gradient surface.…”

Section: Stereo-refraction Methodsmentioning

confidence: 99%

“…Numerous optical measurement methods have been developed at the Institut PPRIME and at the Institut XLIM for the measurements of solid or fluid surfaces. These methods include stereo-correlation or stereo-refraction for fluid interface [1], solid surface measurement by mark tracking, moiré or structured light projectionas well as multisource photometric measurements [2]. The first part of the paper presents the basic principles of these different methods and recent proposed improvements.…”

Section: Introductionmentioning

confidence: 99%

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Development of optical methods for surface and volumetric measurements

Gomit

Thomas

Chatellier

et al. 2017

18th International Congress of Metrology

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Abstract. Optical metrology includes a set of non-contact measurement methods to quantify shapes, surfaces, distances, deformations, displacements or colorimetry. Optical measurement methods have the advantage of being non-intrusive while allowing instantaneous measurements over extended areas. The applications of optical metrology concern all fields of engineering. The paper presents developments related to surface and to 4D measurements (3D displacements + time). Different methods in the fields of solid and fluid mechanics are described and are illustrated by applications. Their applications in different fields for static or dynamic measurements and the limits is discussed in the paper.

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Section: Stereo-refraction Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Development of optical methods for surface and volumetric measurements

Gomit

Thomas

Chatellier

et al. 2017

18th International Congress of Metrology

Self Cite

View full text Add to dashboard Cite

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“…The changes in the projected pattern due to changes in the surface are registered by the camera. Changes in a free water surface have also been measured with this technique (Cang et al 2019;Gomit et al 2013).…”

Section: Introductionmentioning

confidence: 99%

High-resolution single-camera photogrammetry: incorporation of refraction at a fluid interface

et al. 2019

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Photogrammetry uses images of a three-dimensional structure to derive information about its shape and position. In this work, a photogrammetric technique is implemented with a single camera and a digital projector to measure changes in an underwater sediment bed. This implementation incorporates refraction at an interface allowing for measurements through a deformed or changing water surface. The digital projector provides flexibility in choosing projected patterns and has a high frame rate, which allows to easily increase the spatial and temporal resolution of the measurements. The technique requires first for both the camera and the projector to be calibrated using triangulation. With the calibration, we construct lines in three-dimensional space that originate from the projector and the camera, and intersect on the surface to be measured. To correctly incorporate refraction due to a change of medium, each line in space is recalculated from its intersection with the interface using Snell's law. This has the benefit that only one calibration for measurements is needed if the location and shape of the interface are known. The technique is validated by measuring a submerged undulated surface, plastic objects and a sediment bed. In particular, the undulated plate is reconstructed under a flat and a parabolic water surface. Finally, the technique is used in combination with particle image velocimetry to dynamically measure a changing sediment bed under an oscillating flow and the flow velocity at the free surface.

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“…Differences in PIV measurements from the two cameras are attributed to light refraction at the free surface, such that the free surface may be reconstructed based on the difference between the PIV measurements. This technique is extended by Gomit, where refraction at the free surface is measured using a stereo camera system to reconstruct the free surface, with velocity measured in a two-dimensional slice below the free surface in the wake of a towed ship model [12].…”

Section: Introductionmentioning

confidence: 99%

“…The techniques implemented by Fouras and Gomit are very useful in obtaining free surface and velocity field measurements at the same time, however, extending these techniques to measure velocity fields throughout the fluid volume poses challenges [11,12]. For example, near the free surface, intersection of the laser sheet with the free surface can distort the laser sheet, inhibiting PIV measurements.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Measurement of Free Surface Elevation and Three-Component Velocity Field Around a Translating Surface-Piercing Foil

Schock

Dahl

2018

Journal of Offshore Mechanics and Arctic Engineering

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Two methods are investigated to simultaneously obtain both three-dimensional (3D) velocity field and free surface elevations (FSEs) measurements near a surface piercing foil, while limiting the equipment. The combined velocity field and FSE measurements are obtained specifically for the validation of numerical methods requiring simultaneous field data and free surface measurements for a slender body shape. Both methods use stereo particle image velocimetry (SPIV) to measure three component velocities in the flow field and both methods use an off the shelf digital camera with a laser intersection line to measure FSEs. The first method is performed using a vertical laser sheet oriented parallel to the foil chord line. Through repetition of experiments with repositioning of the laser, a statistical representation of the three-dimensional flow field and surface elevations is obtained. The second method orients the vertical laser sheet such that the foil chord line is orthogonal to the laser sheet. A single experiment is performed with this method to measure the three-dimensional three component (3D3C) flow field and free surface, assuming steady flow conditions, such that the time dimension is used to expand the flow field in 3D space. The two methods are compared using dynamic mode decomposition and found to be comparable in the primary mode. Utilizing these methods produces results that are acceptable for use in numerical methods verification, at a fraction of the capital and computing cost associated with two plane or tomographic particle image velocimetry (PIV).

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Free surface measurement by stereo-refraction

Cited by 61 publications

References 18 publications

Development of optical methods for surface and volumetric measurements

Development of optical methods for surface and volumetric measurements

High-resolution single-camera photogrammetry: incorporation of refraction at a fluid interface

Simultaneous Measurement of Free Surface Elevation and Three-Component Velocity Field Around a Translating Surface-Piercing Foil

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