Granular pesticide distribution pattern from a helicopter-borne spreader

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Ghimire, Mahesh
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A simulation program which could predict the ground deposition pattern of material applied from a air-borne spreader is a prerequisite for developing a control system to vary the flow of the chemical. Deposition pattern could be determined by conducting test in which an air-borne spreader is flown over an array of collectors on the ground and the material collected in each collector is measured. However, the high cost of conducting a field test, and uncertainties involved in such tests justify the simulation study. A mathematical model is first developed to predict the behavior of a particle ejected from an aircraft. Computer programs are developed to simulate (i) particle trajectories and, (ii) dry material distribution patterns from a class of helicopter-borne spreader. The aircraft speed, particle size and density, and, the atmospheric wind are found to have significant effect on the deposition uniformity and pattern width. The altitude of the flight is found to have only marginal effect. Field tests arethen conducted to find the actual deposition pattern on the ground and the results are analyzed. Field tests are found to be associated with high degree of uncertainty in terms of variable inputs. Comparison of the experimental patterns with the simulated ones is conducted. The model is found to have potential in predicting the trends in change of deposition pattern shape and size with changes in variables like particle properties, aircraft speed, altitude and wind speed.