ased on the assumption that when particle motion is dominated by collision interactions, notions from gas kinetic theory can be exploited to deal with the turbulence resulting from particle streaming (kinetic contribution) and direct collisions (collision contribution) (ref kinetic theory: "Derivation, implementation, and validation of computer simulation models for gas-solid fluidized beds", B.G.M. van Wachem, Ph.D. Thesis, Delft University of Technology, Amsterdam, 2000)