Complémentarité des outils de saisie de texte en environnement virtuel immersif

Cette étude présente un test utilisateur afin de déterminer quels sont les avantages et inconvénients de différents modes de saisie de texte en environnement virtuel immersif : la reconnaissance vocale individuelle, la reconnaissance vocale collective et le clavier virtuel surnommé Drum-Like Keyboard. Nous avons mesuré l’expérience utilisateur des participants notamment selon l’utilisabilité et l’utilité afin de pouvoir proposer des recommandations adéquates aux personnes cherchant à intégrer la saisie de texte en réalité virtuelle. Nos résultats montrent que la reconnaissance vocale et le clavier virtuel ont des qualités complémentaires, qui peuvent être utilisées de concert pour obtenir des résultats et une expérience optimale.Fondation Arts et Métier

Text input tools’ complementarity in immersive virtual environments

This study presents a user test in order to ascertain the advantages and disadvantages of three different text input methods in immersive virtual environment: individual Speech-to-Text, collective Speech-to-Text and a virtual keyboard named Drum-Like Keyboard. We measured participants’ user experience, especially related to usability and utility, in order to offer relevant recommendations to people seeking to integrate text input in virtual reality. Our results show that Speech-to-Text and the virtual keyboard have complementary qualities, which can be used together for optimal results and experience

Preferential Paths of Air-water Two-phase Flow in Porous Structures with Special Consideration of Channel Thickness Effects.

Accurate understanding and predicting the flow paths of immiscible two-phase flow in rocky porous structures are of critical importance for the evaluation of oil or gas recovery and prediction of rock slides caused by gas-liquid flow. A 2D phase field model was established for compressible air-water two-phase flow in heterogenous porous structures. The dynamic characteristics of air-water two-phase interface and preferential paths in porous structures were simulated. The factors affecting the path selection of two-phase flow in porous structures were analyzed. Transparent physical models of complex porous structures were prepared using 3D printing technology. Tracer dye was used to visually observe the flow characteristics and path selection in air-water two-phase displacement experiments. The experimental observations agree with the numerical results used to validate the accuracy of phase field model. The effects of channel thickness on the air-water two-phase flow behavior and paths in porous structures were also analyzed. The results indicate that thick channels can induce secondary air flow paths due to the increase in flow resistance; consequently, the flow distribution is different from that in narrow channels. This study provides a new reference for quantitatively analyzing multi-phase flow and predicting the preferential paths of immiscible fluids in porous structures

Prediction of permeability and formation factor of sandstone with hybrid lattice Boltzmann/finite element simulation on microtomographic images

In Fontainebleau sandstone, the evolution of transport properties with porosity is related to changes in both the size and connectivity of the pore space. Microcomputed tomography can be used to characterize the relevant geometric attributes, with the resolution that is sufficiently refined for realistic simulation of transport properties based on the 3D image. In this study, we adopted a hybrid computation scheme that is based on a hierarchical multi-scale approach. The specimen was partitioned into cubic sub-volumes for pore-scale simulation of hydraulic permeability and formation factor using the lattice Boltzmann method. The pore-scale results were then linked with finite element simulation in a homogenized scheme to compute and upscale the transport properties to specimen scale. The simulated permeability and formation factor have magnitude and anisotropy that are in good agreement with experimental rock physics data. Together with simulated and measured values of connected porosity and specific surface area, they provide useful insights into how pore geometry controls the evolution of the transport properties

Three-dimensional imaging of porous media using confocal laser scanning microscopy

Summary In the last decade, imaging techniques capable of reconstructing three-dimensional (3-D) pore-scale model have played a pivotal role in the study of fluid flow through complex porous media. In this study, we present advances in the application of confocal laser scanning microscopy (CLSM) to image, reconstruct and characterize complex porous geological materials with hydrocarbon reservoir and CO2 storage potential. CLSM has a unique capability of producing 3-D thin optical sections of a material, with a wide field of view and submicron resolution in the lateral and axial planes. However, CLSM is limited in the depth (z-dimension) that can be imaged in porous materials. In this study, we introduce a ‘grind and slice’ technique to overcome this limitation. We discuss the practical and technical aspects of the confocal imaging technique with application to complex rock samples including Mt. Gambier and Ketton carbonates. We then describe the complete workflow of image processing to filtering and segmenting the raw 3-D confocal volumetric data into pores and grains. Finally, we use the resulting 3-D pore-scale binarized confocal data obtained to quantitatively determine petrophysical pore-scale properties such as total porosity, macro- and microporosity and single-phase permeability using lattice Boltzmann (LB) simulations, validated by experiments. Lay description In this study, a method is described to apply confocal laser scanning microscopy (CLSM) to image, reconstruct and characterize statistically the 3-D pore space of geological rock samples. Confocal Laser Scanning Microscope has a unique capability of producing very thin optical sections of a material, with submicron resolution in the lateral and axial planes. The limitation of CLSM is the restriction on acquiring depth (z-dimension) information because the observed light intensity is attenuated with depth due to absorption and scattering by the material. It is an extension of the methods currently used in digital rock imaging to build numerical rock models using various techniques, including reconstruction made from computed tomography (CT) scans (micro-CT and synchrotron-computed micro-tomography), computer-generated sphere packs and 2-D scanning electron microscope (SEM) images. The novel method disclosed here is to image the pore space to the depth which can be accessed by the conventional CLSM approach and then grind away a slightly smaller layer of the rock followed by another imaging step. This process is repeated to acquire a 3-D image of unlimited depth. It has an advantage over sequential grinding and 2-D imaging by conventional microscopy in that far fewer grinding steps are needed. It can also be used to acquire an arbitrarily wide image without the loss of resolution by stitching together multiple scans. Micro-CT cannot obtain such a wide field of view without loss of image quality in large physical specimens. The volumetric pore space image obtained in this way can be used to quantitatively predict the macroscopic petrophysical properties, including total porosity, macroporosity, and microporosity and subsample single-phase permeability using known digital rock analysis techniques

Convex hull approach for determining rock representative elementary volume for multiple petrophysical parameters using pore-scale imaging and Lattice-Boltzmann modelling

In the last decade, the study of fluid flow in porous media has developed considerably due to the combination of X-ray Micro Computed Tomography (micro-CT) and advances in computational methods for solving complex fluid flow equations directly or indirectly on reconstructed three-dimensional pore space images. In this study, we calculate porosity and single phase permeability using micro-CT imaging and Lattice Boltzmann (LB) simulations for 8 different porous media: beadpacks (with bead sizes 50 µm and 350 µm), sandpacks (LV60 and HST95), sandstones (Berea, Clashach and Doddington) and a carbonate (Ketton). Combining the observed porosity and calculated single phase permeability, we shed new light on the existence and size of the Representative Element of Volume (REV) capturing the different scales of heterogeneity from the pore-scale imaging. Our study applies the concept of the ‘Convex Hull’ to calculate the REV by considering the two main macroscopic petrophysical parameters, porosity and single phase permeability, simultaneously. The shape of the hull can be used to identify strong correlation between the parameters or greatly differing convergence rates. To further enhance computational efficiency we note that the area of the convex hull (for well-chosen parameters such as the log of the permeability and the porosity) decays exponentially with sub-sample size so that only a few small simulations are needed to determine the system size needed to calculate the parameters to high accuracy (small convex hull area). Finally we propose using a characteristic length such as the pore size to choose an efficient absolute voxel size for the numerical rock

Impact d'un cylindre vertical sur la dynamique sédimentaire sous l'action d'un courant

This work concerns the study of sediment patterns formation downstream a vertical cylinder under a steady current. The cylinder simulates an offshore monopile foundation, or a bridge pile. A theoretical modeling is developed. The results are in good agreement with the experimental results obtained in the framework of this PhD. An experimental and theoretical preliminary study on sediment segregation in the vicinity of the cylinder is also performed.Les travaux portent sur l’étude de la formation de motifs sédimentaires à l’aval d’un cylindre vertical soumis à un courant. Le cylindre simule une fondation monopieu d’éolienne en mer, ou une pile de pont. Une modélisation théorique est développée. Les résultats obtenus sont en bon accord avec les résultats expérimentaux acquis au cours de la thèse. Une étude préliminaire expérimentale et théorique sur le tri sédimentaire au voisinage du cylindre est également effectuée