On the formulation of Lagrangian stochastic models for heavy-particle trajectories

The modeling approach of B. L. Sawford and E H. Guest ("8th Symposium of Tu rbulence and Diffusion; San Diego, CA," ;pp. 96-99. Am. Meteorol. Soc., Bos ton, MA, 1990) is extended to encompass the formulation of Lagrangian stoch astic models for fluid velocities along heavy-particle trajectories in inho mogeneous turbulent flows. The approach ensures consistency with prescribed Eulerian fluid velocity statistics. Models are formulated and then used in conjuction with the equations of motion for heavy particles to simulate th e trajectories of heavy particles in vertical turbulent pipe how Model pred ictions for particle-velocity statistics, particle deposition velocities, a nd mean particle concentrations are shown to be in good agreement with expe rimental results. In contrast with "eddy-interaction" models but in accord with the results of direct numerical simulations, the models predict a buil dup of mean particle concentration within the viscous sublayer at y(+) appr oximate to 0.2. It is suggested that Lagrangian stochastic models for fluid -particle motions provide a good description of fluid velocities along the trajectories of heavy particles, when Lagrangian timescales are appropriate ly modified. (C) 2000 Academic Press.