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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Publications at this Location » Publication #176818

Title: DRIFTSIM - Predicting Drift Distances of Spray Droplets

item Zhu, Heping
item Fox, Robert

Submitted to: Software and User Manual Public Release
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2005
Publication Date: 7/25/2005
Citation: Zhu, H., Fox, R.D., Ozkan, E. 2005. Driftsim - Predicting Drift Distances of Spray Droplets. Software and User Manual Public Release.

Interpretive Summary: Drift from pesticides has, in some cases, caused pollution of the environment and danger to humans. Accurate and rapid determination of spray drift has been a concern for many years. Many field experiments have been conducted to measure spray drift from various applications. Field experiments, however, have the limitation that weather conditions, especially wind, cannot be controlled throughout the test period and can vary during a single pass with a sprayer. Computer simulation provides a means of determining the relative effects of various factors on spray drift. Commercially available computer programs that can predict spray drift and deposition are expensive and require computer operators with special skills to run the programs. A spray droplet drift simulation program was developed to predict the drift distances of spray droplets for a wide range of conditions including droplet size, discharge velocity and height, wind velocity, relative humidity and temperature. The program, which is the only spray drift estimation software that works on portable computers, enables researchers to predict and calculate spray drift potentials which previously was not possible. Extension agencies and researchers can use the program to evaluate spray drift problems and train spray operators to adjust sprayer settings to improve the application performance.

Technical Abstract: Computer simulation provides a means of determining the relative effects of various factors on spray drift while field experiments to measure spray drift have the limitation that many variables cannot be controlled. A Windows Version computer program (DRIFTSIM) was developed to rapidly estimate the mean drift distances of water droplets discharged from atomizers on field sprayers. This program interpolates values from a large data base of drift distances originally calculated for single droplets with a flow simulation program (FLUENT). The simulations of drift distances up to 200 m (656 ft) included temperatures (10-30 °C; 50-86°F), discharge heights (0-2.0 m; 0-6.56 ft), initial downward droplet velocities (0-50 m/s; 0-164 ft/s), relative humidity (10-100%), wind velocities (0-10.0 m/s; 0-32.8 ft/s), droplet sizes (10-2000 µm), droplet size distribution in Dv.1, Dv.5 and Dv.9, and 20% turbulence intensity. Variables can be either in metric or English units. For the input of droplet size distribution, drift distances are reported along with portion of volume in each class such as provided by many droplet size analyzers. The accuracy of the program FLUENT was verified with a uniform droplet generator and wind tunnel. The program indicates the relative effects of the input variables on drift distances and should, especially for large droplets, provide reasonable accuracy for many field applications.