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Author Larbi, Peter Ako
Title Development of a model to predict spray deposition in air-carrier sprayer applications
book jacket
Descript 192 p
Note Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page:
Adviser: Masoud Salyani
Thesis (Ph.D.)--University of Florida, 2011
A simulation model was developed to predict on-target spray deposition when using an airblast sprayer. It was developed as a compartment model where, at a discrete location in the sprayer's travel direction, the plume or spray cloud is handled as passing through several connected compartments of equal thickness but increasing cross section, in the direction of application. With this approach, the spaces between the sprayer and tree and within the canopy were divided into small elements to achieve the needed simplification for simulation purposes. The model, which accounts for evaporation, drift, and ground deposition, simulates spray mass dispersion, assuming no slip between spray droplets and airstream and no contribution to sprayer air velocity from spray droplets. The tree canopy equations account for foliage distribution within a canopy in the direction of spray application, which simultaneously represents resistance to spray transport resulting in deposition. With the incorporation of maximum deposition, it is possible to account for spray runoff from leaves. Two field experiments were conducted to validate the model in two parts, namely: dispersion and deposition. The dispersion experiment setup consisted of a Polyvinyl Chloride pipe structure that provided a grid of five target distances from sprayer outlet and four sampling heights. Absorbent paper targets were used to sample airborne spray from a conventional airblast sprayer. In the deposition experiment, twenty 3-tree plots in an orange grove were sprayed and leaves sampled from the middle tree on two sampling lines at two sampling heights and four canopy depths. Ground samples were also collected. In both experiments, spray treatments consisting of combinations of two nozzles (Albuz ATR Lilac and Albuz ATR Blue nozzles) and two forward speeds (2.4 and 4.8 km/h) were applied using a conventional airblast sprayer. In both experiments, samples were analysed by fluorometry and the total leaf area of each sample from the deposition experiment measured with an area meter. The results showed good agreements between the model output and the experimental data with best predictions in the first case yielding modeling efficiency (EF) and correlation coefficient (r) of 78% and 0.90 for airborne spray and 50% and 0.62 for ground deposits, respectively. The second case yielded EF = 61% and r = 0.92 for canopy deposition, but ground deposition data was overly under-predicted by more than three orders of magnitude and was not considered appropriate. Despite shortcomings, the model has potential for meeting the set objectives, and has been implemented in an expert system to assist spray applicators in making decisions critical for efficient spray operations
School code: 0070
Host Item Dissertation Abstracts International 73-06B
Subject Applied Mathematics
Engineering, Computer
Engineering, Agricultural
Alt Author University of Florida
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