TURBULENT DISPERSION OF PARTICLES - THE STP MODEL

A mathematical description of the stochastic transport of particles (STP) model for particle dispersion in turbulent flows is presented. The STP model is based on established theories of stochastic process modeling. The parameters of the model include physical properties of the particle (diameter and mass) and a description of the turbulent characteristics (mean velocities with root mean square fluctuations and their residence-time correlations) of the fluid phase in which the particles are dispersed. The model includes no adjustable parameters in the sense of calibration factors. It is independent of any particular turbulence model, but estimates of its parameters from information available from the common k-epsilon turbulence model are presented. Elements of the STP model are compared with exact solutions of the diffusion equation, alternative dispersion models, and experimental data collected under well-defined conditions. The STP model reproduces the exact solutions when both are based on consistent assumptions. Suggested approximated terms in the model also reproduce the experimental data nearly within its error under simple flow conditions. The STP model describes the origin of more complex behavior (counter-gradient diffusion, for example) and has the potential of describing it if sufficient detail about the gas-phase turbulence is known.