Granular materials involve a host of operations as part of the normal functioning of society. Example operations include the cultivation and shipping of huge volumes of construction materials (sand, gravel), agricultural and industrial processing of bulk goods (grains, nuts), and even the manipulation of soils upon which all buildings and infrastructure reside. Potentially vast improvements to society can be realized by gaining new insights into the behavior of granular materials, and corresponding gains in efficiency for said operations. The Computer Laboratory for Granular Physics Studies focuses on advancing the understanding of the fundamental nature of interactions between granular objects. Particular emphases are placed on characterizing the phenomenon of friction for granular soils and for modeling the introduction of structural objects into granular media across multiple scales. The laboratory aims to leverage such advances toward improving civil, industrial, and materials engineering processes.
Contours of XY-displacement in LS-DYNA
The physical testing program studies granular material at various scales ranging from nanoscopic surface structures to overall macroscopic behavior. The goal of these physical test are to help determine parameters used in contact models along with providing physical results of macroscopic behavior for comparison with numerical models. As part of the testing program a catalogue of granular material of various sizes, shape and roundness is available.
Atomic force microscope measuring sphere topograph
Modeling of interactions between granular materials and structural (or relatively rigid) objects is essential to investigating the introduction of manmade objects into granular media. For example, current research being carried out at the Computer Laboratory for Granular Physics includes prediction of penetration depths of unexploded ordinance into granular soils. A major research task involves centrifuge testing, which permits scale models to be investigated while maintaining direct, quantitative mappings to behaviors that would be expected at full scale. Further, air gun blast experiments, as associated with penetrations into granular media, are being incorporated directly into (and simultaneous to) the centrifuge operation. During testing, the centrifuge container is filled to the desired height with a granular material of interest and the container is rotated (spun) about the originating end of the arm until a desired centripetal acceleration is achieved. Subsequently, the projectile is fired from the air gun barrel and penetrates some distance into the granular medium. Concurrent modeling efforts will enable the research group to characterize behaviors such as stress wave propagation, evolution of granular contact force networks (force chains), which are not practical measure under (physical) laboratory settings. Ultimately, insights into such behaviors permit unprecedented levels of insight for interactions between structural objects and granular media.
Projectile fired into centrifuge of granules
The subject of macrotransport processes encompasses a broad range of macroscale volume-averaged transport phenomena in continuum-based descriptions of multiple-phase multiple-species geosystems subjected to prescribed boundary and initial conditions. Problems previously addressed and currently being investigated within the scope of the Granular Lab cover the following fields of study: heat and mass transfer in heterogeneous multi-phase porous media; advective-diffusive-reactive transport phenomena in capillary networks arising in granular systems (such as in packed-beds); and, contaminant dispersion in natural water systems. The primary application is resolution of multidimensional multi-phase multi-species macrotransport processes in multiplicity of time and space (i.e., multiple scales). Thus, the scale-dependency of rate-controlling physicochemical processes is considered in the detailed solution of pertinent partial differential equations governing macrotransport phenomena in the particular systems subjected to specified boundary and initial conditions.
2D Porous medium with heat flux