Lagrangian aspects of turbulent transport in pipe flow

A Lagrangian analysis of the turbulent dispersion process was examined by observing the motion of suspended particles in a turbulent flowing liquid. The liquid, trichloroethylene, was pressure-driven through a 0.0254 meter (1 inch) I.D. glass pipe. A photographing technique was developed which enabled the photographing of particle motion over large distances. Particle positions in time were computed from the photographic images. Lagrangian time correlations were computed from the displacement and velocity deviations obtained from the particle trajectories. The time dependence of the various correlations was obvious from an examination of the plotted results. The effect of a confining wall on the radial spread of the particles was apparent for large times. It appeared that the assumption of a constant radial eddy diffusivity coefficient could be used as a fair approximation of the time-dependent coefficient.