A PARTITIONED ENERGY-TRANSFER MODEL FOR SPRAY IMPACTION ON PLANTS

Of the processes active in foliar spray application of pesticidal and biologically active compounds in agriculture, impaction and deposit formation have been relatively neglected topics of investigation. Experimental research on spray-dynamic phenomena at the plant interface shows that rebound of droplets from some plant surfaces is a significant factor limiting effective application and retention. An energy transfer model was developed which predicts probable reflected velocity factors, or coefficients of restitution, for the first-impact rebound of droplets from a plant surface. The model, based on the principle of equipartition of energy as a limiting case, requires uniform distribution of incoming kinetic energy, on the average, among the dimensions of energy transfer modes involved. Energy transfer modes identified include droplet and plant-surface elastic deformation, impulse or shock, and plant-surface alteration. Available energy from elastic deformations is partitioned among droplet translation, rotation, oscillatory and internal energies when rebound occurs. The model will help determine the most effective ways to modify energy transfer in order to limit droplet rebound and improve spray retention. © 1991 Silsoe Research Institute.