G90-1001 Spray Drift of Pesticides

Crop Protection, 2015

Spray drift is a consideration for growers and applicators who are increasingly selecting larger droplet producing nozzles to allay their concerns. As new technologies arrive on the market, the prices of individual nozzles have risen which puts a greater need for consistency among nozzles to be worth the investment. These nozzles, while effective at reducing spray drift, may not always be consistent at maintaining efficacy which can be a result of a lack of uniformity in the production of these nozzles. Twenty-one spray drift reducing nozzles were compared for droplet size distributions across three liquids of varying dynamic surface tensions in a wind tunnel at the University of Queensland. Research sought to identify the repeatability of each nozzle type by randomly selecting five units to test consistency of droplet size measurements across nozzle type. Results indicate that some nozzle types are consistent and repeatable while others are not. It was also observed that some nozzle types are relatively unaffected by liquid type, where others resulted in a droplet size change in volume median diameter (VMD) of 100 mm depending on liquid type at the same operating pressure. Research from this study will help growers and industry to select the best nozzle types to ensure uniformity of application, to maximize efficacy and to reduce pesticide spray drift.

Fluids

The condition for the formation of droplet groups in liquid sprays is poorly understood. This study looks at a simplified model system consisting of two iso-propanol droplets of equal diameter, Dd0, in tandem, separated initially by a center-to-center distance, a20, and moving in the direction of gravity with an initial velocity, Vd0>Vt, where Vt is the terminal velocity of an isolated droplet from Stokes flow analysis. A theoretical analysis based on Stokes flow around this double-droplet system is presented, including an inertial correction factor in terms of drag coefficient to account for large Reynolds numbers (≫1). From this analysis, it is observed that the drag force experienced by the leading droplet is higher than that experienced by the trailing droplet. The temporal evolutions of the velocity, Vd(t), of the droplets, as well as their separation distance, a2(t), are presented, and the time to at which the droplets come in contact with each other and their approach velo...

In pesticide applications, small droplets are desired for better coverage and uniform distribution. Therefore, small droplets are generally more effective than large droplets. Yet, small droplets have a problem: drift, i.e., the movement of droplets off-target. Two types of drifts cause chemicals to move off-target: particle drift and vapor drift. Particle drift occurs through the deposition of chemical particles outside the intended target area. Vapor drift occurs through the dispersion of vaporized chemical to the atmosphere and areas surrounding the target area during and following application. A number of factors influence drift, including meteorological conditions (wind speed, temperature, humidity, and evaporation), topography, crop or area being sprayed, application equipment and methods, and decisions by the applicator.

2005 Tampa, FL July 17-20, 2005, 2005

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 D v.1 , D v.5 and D v.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.

Journal of Agricultural Science and Technology B, 2015

Spray drift has become an important issue in pesticide application. Vineyard spraying is particularly interesting to consider, as pesticide droplets are not directed towards the ground but rather towards the targeted crop. The aim of this study was to investigate the influence of nozzle orientation on droplet size and droplet velocity using three different nozzles (IDK, TVI and TXA) used in vineyards. Two series of measurement were performed in order to assess the effect of the gravity on sprays. Droplet size and one-dimensional droplet velocity characteristics were measured using a phase Doppler particle analyser (PDPA). Two planes, i.e., one horizontal and one vertical, were considered. Results suggest that the nozzle orientation slightly affects the size distribution, which is shifted towards larger droplets when nozzles spray horizontally compared to vertically spray. However, droplet axial velocity distribution is shifted towards lower values. Supposing that the only droplets which can reach the crop are those with an axial velocity greater than 1 m/s and a diameter larger than 100 µm, results showed significant differences according to the nozzle and orientation. More than 98.6% of the spray volume would reach the target whatever the orientation of the IDK nozzle, 78.8% of the spray volume would reach the crop when the TVI nozzle sprays horizontally, while only 16.0% of the spray volume would reach the crop when TXA nozzle sprays horizontally. This paper offers new perspectives in the comprehension and the optimization of the deposition process into the vegetation based from droplet size and velocity profiles from horizontally oriented sprays from flat fan or hollow cone nozzles.

EPJ Web of Conferences, 2014

Time resolved droplet size and velocity measurement was made using Phase-Doppler anemometry in an effervescent spray at GLR of 6 % and operation pressure drops 21 -52 kPa. The spray shows a size dependent variation of mean as well as fluctuating axial and radial velocities of droplets similarly for all operation regimes. Particles under 13 μm follow the gas flow, axially decelerated due to gas expansion. Velocity of medium sized particles is positively size correlated and larger particles keep high velocity, given them during discharge. Fluctuating radial velocity of small particles is larger than that of large particles while fluctuating axial velocity increases with size. Small particles thus reach a ratio of radial to axial velocity fluctuations ~ 0.6 but large particles only ~ 0.1, which indicates large transverse dispersion of small particles. Overall fluctuating velocity ratios smaller than 0.5 document an anisotropic character of the liquid mass fluctuations. Power spectral density (PSD) of axial velocity fluctuations of large droplets is uniform up to 1 kHz, while PSD of smaller particles drops down with frequency for frequencies > 100 Hz. Large particles thus preserve the fluctuations imposed during discharge while the gas turbulence drops with frequency. Turbulence intensity reaches 14 to 21 % depending on pressure. Such high-turbulence character of the flow probably results from a heterogeneous gas-liquid mixture at the discharge. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Applied Research Agrotechnology, 2013

There are several factors that influence in the coverage percentage of the target: spray equipments, spray nozzle, adjuvants, weather conditions, soil topographic, etc. Based on this aspect, the uniformity of drop distribution on the target is the goal of the application technology. The aim of this study was to evaluate the horizontal drops distribution of a sprayer. It were distributed 396 water-sensitive papers, with a spacing of 1 m each, in a plain area of 12 x 33 m. Upon such papers was applied water through a hydraulic sprayer with 12 meters of bars. After the application, the water-sensitive papers were digitalized in a scanner and the obtained imaged analyzed the percentage of coverage by the Conta-Gotas ® software. The data obtained were integrated and arranged in graphic, generating an image with five bands of coverage (0-20, 20-40, 40-60, 60-80 and 80-100%). It was verified a wide variation in the percentage of coverage along the pulverized area. The most part of the area (87.09%) had coverage between 40% and 80%. Thus, the results showed that even under appropriate operating conditions, applications with sprayer may not show uniformity.

SAE Technical Paper Series, 1990

for copying beyond that permitted by Sections 107or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Service Department. To obtain quantity reprint rates, permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. AN MSAE pper aft. abstracted &nd ndexed in ______ "_ _ the SAE Gjob AAMowry Database. "R GLOM. MOILr'Y OATA3ASE No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.

2019

This study presents an experimental study of splashing droplets in spray impact phenomena. The obtained results indicate that the growth rates for crown base radius and crown height for a splashing droplet in a spray are significantly different than that of a single or train of single droplets impacting onto an undisturbed liquid layer. The dimensionless time required for development of the crown base radius takes about 70% longer in compare to the crown height development. Also results obtained in this study indicate that non-dimensional crown height increases linearly with Weber number before the impact.