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One of the major shortcomings of discrete element modelling (DEM) is the computational cost required when the number of particles is huge, especially for fine powders and/or industry scale simulations. This study investigates the scaling of model parameters that is necessary to produce scale independent predictions for cohesionless and cohesive solid under quasi-static simulation of confined compression and unconfined compression to failure. A bilinear elasto-plastic adhesive frictional contact model was used. The results show that contact stiffness (both normal and tangential) for loading and unloading scales linearly with the particle size and the adhesive force scales very well with the square of the particle size. This scaling law would allow scaled up particle DEM model to exhibit bulk mechanical loading response in uniaxial test that is similar to a material comprised of much smaller particles. This is a first step towards a mesoscopic representation of a cohesive powder that is phenomenological based to produce the key bulk characteristics of a cohesive solid and has the potential to gain considerable computational advantage for industry scale DEM simulations.Paper published in Powder Technology (2015)-use for reference/citation

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If gas-adsorbate momentum transfer is ignored, calculated surface fluxes within porous materials often can be grossly incorrect. Methods are introduced for including these interactions when calculating surface fluxes in permeability studies. Developments are carried out for systems with porous materials having both uniform and heterogeneous surfaces. These methods complement one developed earlier for Wicke-Kallenbach experiments, using porous materials with uniform surfaces. Some previous studies are then considered. In one system, including gas-adsorbate momentum transfer changes the proposed surfacediffusion mechanism_from a "hopping" phenomenon to the mobility inherent in a two-dimensional gas. Consideration of other systems shows that, while very where they are not. A criterion is developed for indicating when this momentum transfer is significant and its inclusion in surface-flux determinations is necessary. SCOPETransport of a substance within an adsorbed phase is known as surface diffusion; it has the possibility of being important in a variety of fields, such as adsorption, catalysis, and membraneseparation processes. In addition, understanding of this type of transport could give significant insight into the molecular structure of adsorbed phases and how this structure varies as circumstances change. Unfortunately, at the present time, in spite of numerous studies over the last several decades, there still exists no model adequate for predicting the surfacediffusion behavior of an adsorbed phase within a porous material. The best correlation thus far developed can predict a surface-diffusion coefficient to within only about 1% orders of magnitude .One factor which has been ignored in most previous investigations of surface diffusion is the effect of collisions between gas molecules and the mobile molecules in the adsorbed phase. It has been shown recently that momentum transfer during these collisions has two effects which should be important in any study of surface migration in pores. One is concerned with calculating the actual flux of material on the surface. In studies of surface diffusion in porous materials, only the sum of the gas and surface fluxes can be measured, and theoretical considerations are necessary to separate the two components. Taking the momentum transfer between the colliding gas and adsorbate molecules into account in these theoretical considerations can make a significant difference in the calculated surface component of the total flux. The other effect concerns the impact of momentum exchange from these collisions on the migrational behavior of the adsorbed phase.The present work is concerned with the first of these effects--calculation of the surface flux and how considering the momentum transfer during gas-adsorbate collisions will affect this calculation. Surface diffusion over both energetically uniform and nonuniform surfaces is considered. An example illustrates what can happen to earlier conclusions when the original surface fluxes, calculated without taking these collis...