Solid particulate, mechanical behavior

In recent years, DEM has been used in combination with computational fluid dynamics (CFD) aiming at investigating particulate behavior in fluid phase. For a two-phase particle-fluid system, the solid motion and fluid mechanics are solved through the application of Newton s equations of motion for the discrete particles and Navier-Stokes equations for the continuum fluid [2]. 

The particulate materials in solids cause mixing to be complex The particles in such materials are small but finite in size moreover, they are isolated from each other, i.e., they are discrete. These characteristics render particulate materials mesoscopic. In general, the behavior of mesoscopic materials is describable neither by the firmly established laws of continuum mechanics valid for macroscopic materials, e.g., steel beams or large ice cubes, nor by the well-known principles of statistical mechanics applicable to microscopic materials, e.g., air. Any attempt to rigorously portray the motion of a countless number of interacting particles in a mixture by particle dynamics would be futile, as evidenced by the difficulty of portraying the motion of interacting particles as few as three. 

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