Publié le 8 avril 2026
–
Mis à jour le 8 avril 2026
Date(s)
le 9 avril 2026
11h00
Lieu(x)
Institut de Physique de Nice
Salle des séminaires
Salle des séminaires
Rheology and microstructure of unsaturated wet granular materials
Fluid seminars
Abstract:
Unsaturated wet granular materials exhibit intricate microstructure composed of solid particles, liquid phases, and void spaces. Understanding their morphological and rheological characteristics is essential for various applications ranging from geotechnical engineering to environmental science. However, the flow behavior of these materials remains poorly understood due to their inherent complexity, which is compounded by the challenges of experimental instrumentation and the absence of unified theoretical frameworks.
The presentation will focus on experiments and discrete element simulations of homogeneous, simple, normal stress-controlled shear flows of model unsaturated wet granular materials: assemblies of frictional spherical particles bonded by a small quantity of a wetting liquid.
Firstly, the rheology of such unsaturated granular materials in the dense flow regime is characterized in terms of internal friction coefficient $µ*$ and solid fraction $\phi_��$, depending on the reduced pressure $��*$ comparing capillary forces to controlled normal stress and on a visco-inertial number $��$, combining the viscous number $��_��$ with inertial number $��$ as $��= ��_��+2��_2$.
Secondly, the microstructure of such materials is explored using X-ray micro-tomography. Advanced segmentation techniques are employed to overcome challenges in distinguishing phases within the material, utlizing a combination of Random Forest and U-Net models for accurate segmentation of the X-ray images. This methodology enables the quantification of the solid and liquid fractions within the sample, revealing the effects of shear deformation on their distribution.
Additionally, a new automated tool is developed for classifying different liquid morphologies within the liquid phase. We demonstrated the impact of shear deformation on the redistribution and clustering of liquid morphologies.
Moreover, the coordination number is estimated, providing detailed insights into the interactions between solid particles and liquid phases.This work provides a robust methodology for volume characterization and quantitative analysis of complex wet granular material microstructures.
Abstract:
Unsaturated wet granular materials exhibit intricate microstructure composed of solid particles, liquid phases, and void spaces. Understanding their morphological and rheological characteristics is essential for various applications ranging from geotechnical engineering to environmental science. However, the flow behavior of these materials remains poorly understood due to their inherent complexity, which is compounded by the challenges of experimental instrumentation and the absence of unified theoretical frameworks.
The presentation will focus on experiments and discrete element simulations of homogeneous, simple, normal stress-controlled shear flows of model unsaturated wet granular materials: assemblies of frictional spherical particles bonded by a small quantity of a wetting liquid.
Firstly, the rheology of such unsaturated granular materials in the dense flow regime is characterized in terms of internal friction coefficient $µ*$ and solid fraction $\phi_��$, depending on the reduced pressure $��*$ comparing capillary forces to controlled normal stress and on a visco-inertial number $��$, combining the viscous number $��_��$ with inertial number $��$ as $��= ��_��+2��_2$.
Secondly, the microstructure of such materials is explored using X-ray micro-tomography. Advanced segmentation techniques are employed to overcome challenges in distinguishing phases within the material, utlizing a combination of Random Forest and U-Net models for accurate segmentation of the X-ray images. This methodology enables the quantification of the solid and liquid fractions within the sample, revealing the effects of shear deformation on their distribution.
Additionally, a new automated tool is developed for classifying different liquid morphologies within the liquid phase. We demonstrated the impact of shear deformation on the redistribution and clustering of liquid morphologies.
Moreover, the coordination number is estimated, providing detailed insights into the interactions between solid particles and liquid phases.This work provides a robust methodology for volume characterization and quantitative analysis of complex wet granular material microstructures.