This article discusses turbulent dispersion of particles whose size and inertia are such that it cannot be assumed that they will follow exactly the fluctuations of the fluid elements with which they are associated. The turbulent field is assumed to be stationary, homogeneous and isotropic. Stationary, extraneous force fields for the particles may exist. The method of generalized harmonic analysis (Wiener) is used to determine the statistical particle-dispersion parameters in terms of the spectrum density of the turbulent field and the physical characteristics of the particles. The discussion is restricted to one-dimensional problems; it includes consideration of the relation between turbulent dispersion and Brownian motion of the particles due to molecular impacts.
An illustrative example of dispersion calculation with a given turbulence spectrum is presented, and aspects of practical applications are discussed briefly.