VELOCITY STATISTICS OF ROUND, FULLY-DEVELOPED, BUOYANT TURBULENT PLUMES

An experimental study of the structure of round buoyant turbulent plum es was carried out, limited to conditions within the fully developed ( self-preserving) portion of the flow. Plume conditions were simulated using dense gas sources (carbon dioxide and sulfur hexafluoride) in a still air environment. Velocity statistics were measured using laser v elocimetry in order to supplement earlier measurements of mixture frac tion statistics using laser-induced iodine fluorescence. similar to th e earlier observations of mixture fraction statistics, self-preserving behavior was observed for velocity statistics over the present test r ange (87-151 source diameters and 12-43 Morton length scales from the source), which was farther from the source than most earlier measureme nts. Additionally, the new measurements indicated that self-preserving plumes are narrower, with larger mean streamwise velocities near the axis (when appropriately scaled) and with smaller entrainment rates, t han previously thought. Velocity statistics reported include mean and fluctuating velocities, temporal power spectra, temporal and spatial i ntegral scales, and Reynolds stresses.