A LAGRANGIAN MODEL FOR SOLID PARTICLES IN TURBULENT FLOWS

Applying the time series analysis idea to the temporal and spatial fluid velocity correlations, a three-dimensional Lagrangian model for the motion of particles in turbulent flows has been established. This model has been used to simulate the experiments of other workers. The computed results are compared with the experimental data for the particle dispersion, velocity correlations and velocity decay. In the case where the mean turbulent flow has one main direction, this model has been extended to include the Eulerian temporal velocity correlation; a so-called mixed model has been devised. This model has been used to compute particle dispersion in stationary, homogeneous, isotropic and incompressible turbulence. Comparison is made with the theroetical long-time particle diffusion coefficients for cases where the crossing-trajectory effect is important or unimportant. Good agreement is obtained.