Granular systems

M. Bungay, personal communication. Granular Systems, Sacramento, Calif., Nov. 1986. 

For many measurements specific to granular flows, such as velocity profiles, acceleration or of vibrating samples, a laboratory with NMR/MRI expertise is desirable. Therefore, much of the future progress in NMR/MRI studies of granular systems will come from collaborations of granular matter experts with such laboratories that have the expertise in NMR/MRI. 

For a geonet LDCR system, the flow rate for the geonet is determined in the laboratory by using the ASTM D4716 test method, and the value is modified to meet site-specific situations. The geonet flow rate DR is then determined in the same way as for the granular system. No pipe network is needed. 

DPMs offer a viable tool to study the macroscopic behavior of assemblies of particles and originate from MD methods. Initiated in the 1950s by Alder and Wainwright (1957), MD is by now a well-developed method with thousands of papers published in the open literature on just the technical and numerical aspects. A thorough discussion of MD techniques can be found in the book by Allen and Tildesley (1990), where the details of both numerical algorithms and computational tricks are presented. Also, Frenkel and Smit (1996) provide a comprehensive introduction to the recipes of classical MD with emphasis on the physics underlying these methods. Nearly all techniques developed for MD can be directly applied to discrete particles models, except the formulation of particle-particle interactions. Based on the mechanism of particle-particle interaction, a granular system may be modeled either as hard-spheres or as soft-spheres. ... 

In particular, it is established for a granular system (NiFe)x/(Si02)i x [101-104] that in this case Rs is two orders of magnitude larger than R() and can exceed upto four orders of magnitude from Rs obtained in case of a homogeneous metal (x — 1). However, despite the high value of the Hall coefficient in these materials, experiments till now were performed mainly at the metallic side of the percolation transition [101-104]. 

Abatzoglou N. 2005. Prediction of segregation tendency occurrence in dry particulate pharmaceutical mixtures development of a mathematical tool adapted for granular system application. Pharm. Dev. Technol. 1 59-70. 

There are two main approaches for the numerical simulation of the gas-solid flow 1) Eulerian framework for the gas phase and Lagrangian framework for the dispersed phase (E-L) and 2) Eulerian framework for all phases (E-E). In the E-L approach, trajectories of dispersed phase particles are calculated by solving Newton s second law of motion for each dispersed particle, and the motion of the continuous phase (gas phase) is modeled using an Eulerian framework with the coupling of the particle-gas interaction force. This approach is also referred to as the distinct element method or discrete particle method when applied to a granular system. The fluid forces acting upon particles would include the drag force, lift force, virtual mass force, and Basset history force.Moreover, particle-wall and particle-particle collision models (such as hard sphere model, soft sphere model, or Monte Carlo techniques) are commonly employed for this approach. In the E-E approach, the particle cloud is treated as a continuum. Local mean... 

Fu XW, Elliott JA, Bentham AC, et al. Application of X-ray microtomography and image processing to the investigation of a compacted granular system. Part Part Syst Char 2006 23(3-4) 229-236. 

In the particle-based definition of the NDF, we begin at the microscale and write a dynamic equation for the rate of change of the disperse-phase particle properties at the mesoscale. The simplest system, which we consider first, is a collection of interacting particles in a vacuum wherein the particles interact through collisions and short-range forces. Such a system is referred to as a granular system. We then consider a disperse two-phase system, wherein the particles are dispersed in a fluid. 

Consider first a granular system of Np particles in the absence of a surrounding fluid phase. The dynamics of the nth particle can be described by the position of its center of mass X "V... 

For molecular systems, the definition of the temperature includes the particle mass. For granular systems, we will refer to p as the granular temperature. 

---