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Numerous methodologies have been developed to characterize sprinkler irrigation drops with the purpose of improving irrigation efficiency and controlling soil erosion and compaction. This paper presents the laboratory characterization of the morphology and velocity of drops in their free-falling trajectory as influenced by drop diameter and wind speed. For this purpose, a Particle Tracking Velocimetry technique with in-line volumetric illumination was implemented. Hypodermic needles were used to produce droplets of uniform size. Two needle diameters resulted in drops with average diameters of 1.94 and 2.94 mm. Drops were illuminated with a double-pulsed laser beam or a LED lamp. Drop characterization reached an elevation of 4.28 m and occasionally attained terminal velocity. Motion blur was suppressed using a deconvolution filter. Drop equivalent diameter, velocity, chord ratio, canting angle and trajectory angle were determined using an ad-hoc software. The experimental approach led to the measurement of real drop size by illuminating a volume in the capture zone; Drop shape ranged from quasi-sphere to

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A general model for fl ocs settling velocity is still an open fi eld of research in the scientifi c literature. In this work, a reduced model of an aquaculture recirculation tank was used to validate a model for fl oc settling velocity. Cohesive sediments from non-used food and fi sh excreta are a main concern in those tanks design. Excess concentrations of sediments can cause fi sh death or additional costs of energy for aeration. This research is aimed to understand the settling behavior of fl ocs when subjected to a liquid shear rate. A reduced scale model of an aquaculture recirculation tank was build in Plexiglas in order to use particle image velocimetry and particle tracking velocimetry techniques to measure fl uid velocities, solid settling velocities, fl ocs shape and size.Different fl ow rates and solid concentrations were used to develop varied confi gurations in the system; models for fl oc settling velocity based on fractal theory were calibrated. Cohesive sediments from fi sh food were observed in long-term experiments at constant fl uid shear rate in the recirculation tank. A group of 50 images were obtained for every 5 min. Image analysis provided us with fl oc settling velocity data and fl oc size. Using fl oc settling velocity data, fl oc density was obtained for different diameters at equilibrium conditions, after 1 h or larger experiments. Statistical analysis of fl oc velocities for different fl oc sizes allowed us to obtain an expression for the drag coeffi cient as a function of fl oc particle Reynolds number (R ep ). The results were compared with fl oc settling velocity results from different researchers. The model is able to defi ne the general behavior of fl oc settling velocity, which shows a reduction for larger fl ocs that is not taken into account in classical models. Only two parameters of the drag coeffi cient model for a permeable spherical particle are needed to be calibrated, for different types of sediments, in order to have more general applicability.