Modelling The Dynamic Distribution Of Spray Deposits

A mathematical model to estimate the spray distribution of phytopharmaceutical deposits under a spray boom
is proposed. It focuses on the need to take account of the dynamic effects of the forward movement of the
boom. These are related both to the horizontal and vertical boom movement and to the influence of
aerodynamic factors on the nozzle spray distribution.
The distribution of the spray deposits is computed by multiplying the nozzle spray pattern by the time
needed to move from one position to the next. Mathematically, this is expressed by a convolution of the
trajectory function with the nozzle spray pattern function.
The model is validated through a dynamic test bench to reproduce the boom movements observed in the
field. The chosen method to measure the distribution of the spray deposits is a chemical dosage of the sprayed
potassium chloride (KCl) solution collected in Petri dishes. A pulse-width modulation (PWM) nozzle body
fitted on the test bench is used to generate a dynamic distribution of spray deposits from which the dynamic
two-dimensional nozzle spray pattern is reconstructed. This dynamic nozzle spray pattern introduced in the
model allows a far better estimation of the spray deposit distribution to be made than the one obtained using
the static nozzle spray pattern which was computed using filtered back-projection.