A wind tunnel experiment was conducted on turbulent particle diffusion from a continuous point source in several kinds of turbulence fields. The features of concentration fluctuation of the particle diffusion were detected for grid turbulence with R_λ=36 and large-scale turbulence with R_λ=410 excited by an active turbulence generator. Turbulence characteristics were measured by a hot-wire system and a LDV system was used to obtain particle pedestal signals. To analyze the concentration fluctuation fields, time series signals of concentration were translated from discrete pedestal signals of the particles passing through a control volume of the laser beam. The present experiments clarified the concentration fluctuation characteristics for two typical types of the turbulent particle diffusion, i.e., far field diffusion in the small-scale turbulence and near field diffusion in the large-scale turbulence under the effect of the plume's meandering motion.
