Environmental Parameter Effects on the Fate of a Chemical Slick

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Near-field BLEVE overpressure effects: The shock start model

International audienceThis paper presents the results of a small scale experimental study of BLEVE overpressure effects. Testing consisted of a sealed aluminum tube (0.6 L) filled with either water or propane, being heated by a flame until the internal pressure led to catastrophic failure and explosion. Three parameters were controlled during the experiments: the failing pressure, the weakened length on the tube and the fill level. BLEVEs were obtained with tests involving water and propane. Blast gages and optical techniques were used to characterize the shock wave escaping from the failing tube. The results obtained suggest that the lead shock was primarily generated by the vapor space. Overpressure results obtained were compared with the predictions of existing models and found to be in reasonable agreement except for overpressures measured vertically above the cylinder where the overpressures were highest. A prediction model based on only vapor space characteristics was developed. Images show that the shock was fully formed at some distance away from the vessel opening and this was due to the non-ideal opening of the vessel. The model developed was based on the characteristics of the shock when fully formed away from the tube. These characteristics were defined using a combination of imaging, pressure measurements, and predictions from shock tube theory

Application de la granularite laser à la métrologie des microdéplacements

study and development of phase shifting speckle interferometer sensitive to out of plane and in plane deformation. Applications to mechanical testingEtude et developement d'un interferometre speckle a decalage de phase sensible hors plan et dans le plan. Validation sur cas mecanique

Contribution de l ’Optique Appliquée à la Mécanique et aux Sciences des Risques

Au gré de ce manuscrit, ces différentes techniques optiques - ESPI, SI, TVH, DHI, BOS, DIC,PIV, PLIF, PILS1 … - seront décrites avec leurs avantages et inconvénients, et en présentantdes applications dans différents domaines, de la mécanique du solide aux risques, en passantpar le collage et les interactions de projectiles hyper véloce.Cet ouvrage est structuré en techniques cohérentes et incohérentes, tout en précisantqu’actuellement elles sont toutes compatibles avec l’acquisition rapide d’images.Le projet de recherche concerne principalement la caractérisation des risques industriels etplus particulièrement les phénomènes accidentels rapides. Afin de mieux appréhender lesconséquences et la phénoménologie de ces événements, les perspectives de recherche y sontdécrites, notamment en visualisation rapide couplée à différents capteurs ainsi que lapossibilité de mettre en évidence certains phénomènes … invisibles sans transformationoptique adéquate

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International audienceLiquid nematic crystals are nowadays more often used to change the polarization and/or phase and amplitude of impinging light wave. Nematic liquid crystals valves (LCLV) are also called SLM (Spatial Light Modulator) or LCVR (Liquid Crystal Variable Retarder). This paper will show the different steps required to get a procedure (optical mounting and computing software) enabling the use of LCLV in the output beam of the laser coupled with a 3D speckle interferometry set-up. This LCLV generates the phase shifts between the reference and object beams. The calibration set-up is made of a Mach Zender interferometer with the LCLV in one arm. Interference fringes are obtained and recorded with a CCD camera as LCLV voltage is increased. The fringe processing is achieved with a slice analysis in the Fourier domain. Required phase shifts are then implemented in the phase shifting software. The existing set-up already uses a phase shifter composed by a moving mirror driven by a piezoelectric transducer (PZT). Results of the calibration are compared between piezoelectric device and LCVR. The phase shifting rate and resulting phase error shows the main advantages of the LCVR

Phase-shifting digital speckle pattern interferometry: off-the-shelf setup description and application to stainless steel membrane displacement measurements

International audiencePhase shifting digital speckle pattern interferometry (PDSPI) is well suited for micrometric displacement measurements. It is non-intrusive and without contact for the object under investigation. Speckle is generated when a beam of coherent light impinges the surface of an optically rough object. Designing the system with off-the-shelf components implies the full understanding of speckle generation, image acquisition and processing. This paper will describe the main components and their contribution to the final result, from the speckle effect to the unwrapping of the phase. The designed PSDSPI set-up allows the study from small to large areas and can produce quantitative displacement maps using phase shifting principle. As an application the object is a flat circular steel membrane closing a depression chamber. The size of the membrane is about 20 mm in diameter. The membrane deformation is measured using step by step PSDSPI process while decreasing pressure in the chamber. The results show a typical displacement of about 1 μm for 1 mbar. Quantitative profiles of the membrane deformation can be obtained. Further applications will be presented, including measurement corrections by shape of the object. Phase discontinuities will be discussed

Nematic liquid crystals light valve: application to phase shifting speckle interferometry

International audienceLiquid nematic crystals are nowadays more often used to change the polarization and/or phase and amplitude of impinging light wave. Nematic liquid crystals valves (LCLV) are also called SLM (Spatial Light Modulator) or LCVR (Liquid Crystal Variable Retarder). This paper will show the different steps required to get a procedure (optical mounting and computing software) enabling the use of LCLV in the output beam of the laser coupled with a 3D speckle interferometry set-up. This LCLV generates the phase shifts between the reference and object beams. The calibration setup is made of a Mach Zender interferometer with the LCLV in one arm. Interference fringes are obtained and recorded with a CCD camera as LCLV voltage is increased. The fringe processing is achieved with a slice analysis in the Fourier domain. Required phase shifts are then implemented in the phase shifting software. The existing set-up already uses a phase shifter composed by a moving mirror driven by a piezoelectric transducer (PZT). Results of the calibration are compared between piezoelectric device and LCVR. The phase shifting rate and resulting phase error shows the main advantages of the LCVR

Elementary Speckle Interferometry

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Speckle06: Speckles, From Grains to Flowers

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Elementary Speckle Interferometry

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