Effect of spatial inhomogeneity and temporal fluctuation of particle distributions on interparticle collision rate in particulate flows

Direct measurements on the interparticle collision processes in a vertical gas-particle two-phase flow were conducted using high-speed flow visualization and PTV techniques. The commonly-used theoretical model for interparticle collision rate, which was derived from the analogy with kinetic theory of gases, was evaluated by the experimental data. It was shown that the theoretical model markedly overestimated the interparticle collision rate in gas-particle flows. This overestimation was analyzed to be caused by the discrepancies between the model assumptions and the actual particulate flows. One of the most significant factors was the inhomogeneity and fluctuation of particle distributions, which was a general characteristic in actual particulate flows but neglected in the model. The quantitative scales of the inhomogeneity and fluctuation of particle distributions were analyzed by the coefficient of variation and introduced into the interparticle collision rate expression to modify the theoretical model. The estimations by the modified collision rate model agreed well with the experimental data. The modified model was proved to be valid for the analyses of interparticle collisions in actual particulate flows.