Numerical simulation of a coupled nonlinear model for grain coarsening and coalescence

Abstract

A kinetic nonlinear model of mass transfer, grain coarsening and coalescence with potential applications in sintering processes is studied. The model involves nonlinear ordinary differential equations that determine the transport of mass between grains. The rate of mass transfer is controlled by an Arrhenius factor leading to a nonlinear model of mass transfer and grain coarsening. The resulting dynamical system of coupled nonlinear differential equations with random initial conditions (i.e., initial grain mass configuration) is solved by means of the fourth order Runge–Kutta method. We conduct an analysis of the two-grain system and identify three dynamic regimes (diffusive, growth-decay and trapping). The same regimes are shown to persist in the multigrain system. We confirm the numerical performance of the Runge–Kutta method by means of a suitable convergence measure. The influence of the activation energy parameter on the dynamic regimes is investigated. It is shown that as the parameter grows the diffusive regime is progressively restricted to smaller values of the initial grain distribution. We introduce grain coalescence in the mass transfer equations, and we show that it accelerates the growth of the larger grains. Finally, we compare the dynamic evolution of the grain size distribution with the Ostwald ripening expression.