Location: Application Technology Research
Project Number: 5082-21620-001-16-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2019
End Date: Mar 31, 2021
The objective of this research is to use computational fluid dynamics models to develop an advanced computer program to estimate spray droplet displacements and airborne drift potentials resulted from conventional and intelligent sprayers.
A computer program will be developed through computation fluid dynamics (CFD) simulations using a supercomputer to calculate the spray efficiency and spray drift under different application conditions. The computer program will consist of a database of pesticide spray deposition and drift generated by CFD simulations, embedded data analysis and presentation programs, and user friendly graphical interfaces. Parameters in the program include crop type, growth stage, tractor speed, nozzle type, ambient wind speed, air temperature, and relative humidity. In the CFD simulations, a main computational domain will be developed with structured hexahedron cell mashes to simulate field conditions of nurseries, orchards or vineyards. Vertical profiles of wind speeds and turbulence quantities obtained at the outlet of the windward domain will be used as input profiles at the inlet of the main computational domain. Three-dimensional airflow patterns in the domains will be simulated by a CFD model using the Reynolds-averaged Navier-Stokes equations. Crops will be modeled by setting porosity at structured cells where imaginary plants are assumed to be located. Source terms for momentum loss and changes of turbulence kinetic energy and specific dissipation rate due to the crops will be added to the governing equations within the cells of virtual crops. The inlet boundary of the main computational domain will be designed as a combination of the canopy wind profiles and the turbulent air jet by the sprayer. Droplets discharged to the air will be tracked by the Lagrangian discrete phase model, which predicts trajectories of discrete droplets by integrating the inertia with the drag force and the buoyancy force acting on the droplets. Droplets traveling in the air will be destined to sink by being deposited on the ground, being trapped within crop canopies or escaping from the computational domain through the outlet boundary. All droplets that collided with the ground will be assumed as the ground deposition. After the CFD simulation, the history of droplets discharged to the field will be processed which includes the location, particle mass, particle diameter, the number of particles in a parcel, and particle velocity of droplet parcels at the moment of droplet cessation by being deposited on the ground, being captured in the canopy, and escaping through the outlet. An interpolated report will be generated through the drift potential database, data analysis programs, and conditions inputs through graphic interfaces, enabling users to estimate the spray mass balances, spray drift through airborne and ground deposition by distance, and pesticide drift setback distances to prevent the potential risk of spray drift. Field experiments will also be conducted to validate the computer program accuracy for a wide range of pesticide application scenarios in nurseries, apple orchards and vineyards.