Computational Fluid Dynamics Study of the Wake of a High-Clearance Agricultural Boom Sprayer
Date
2022-05-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-4132-2730
Type
Thesis
Degree Level
Masters
Abstract
Self propelled agricultural sprayers are commonly found on farms in Saskatchewan. These
vehicles are used to spray pesticides onto crops to increase the productivity of the field. Spray
drift occurs when pesticides are carried away from their target. It has been estimated that up to
30% of all pesticides sprayed onto a crop will drift. The literature contains multiple studies on
how particles released from a nozzle will travel, but there is a lack of research towards
understanding how the airflow patterns around an agricultural sprayer might affect spray drift.
The present thesis research modeled the airflow around a John Deere 4830 agricultural sprayer
using computational fluid dynamics (CFD), with a focus on the sprayer wake. Since agricultural
sprayers are large vehicles, the numerical grid must include enough elements to realistically
model the wake of the sprayer, while keeping the number of elements low enough to make the
simulations possible in a reasonable amount of time. Several grids with different element size
and type were investigated to meet this requirement. Benchmarking studies were performed on a
circular cylinder to determine the performance of different grids. The best performing grids were
then tested on a small section of the sprayer boom. In the sample boom tests the smaller elements
provided more detail, but there were stability issues, the coarse elements were ultimately chosen
as they performed realistically.
The full-scale simulations were performed using the STAR-CCM+ commercial CFD code.
Using the grid developed earlier, three simulations were performed on the agricultural sprayer.
The three simulations represented different boom heights and sprayer travel speeds to determine
how different operating conditions may affect the airflow around the sprayer. The simulations
showed that the wake of a sprayer has four different zones, corresponding to different parts of
the vehicle and boom geometry.
The wake of the sprayer was shown to be largest directly behind the vehicle. The downstream
extent of the wake decreases along the boom up to the folding knuckle where the size increases
again due to the increased blockage of the flow. The simulations showed that increasing the
sprayer travel speed and increasing the boom height both caused significant increases to the
turbulence intensity in the wake of the sprayer and in the region near the nozzles. This in turn
could increase the potential for spray drift occurring.
Description
Keywords
Computational Fluid Dynamics, Agricultural Spraying, Wakes, Agricultural Sprayer Wake, Spray Drift, Pesticides, CFD, Fluid Mechanics, Simulation
Citation
Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering