Effects of Formulated Glyphosate and Adjuvant Tank Mixes on Atomization from Aerial Application Flat Fan Nozzles
Abstract : This study was designed to determine if the present USDAARS spray-nozzle models, which were based on spray solutions of water plus non-ionic surfactant, could be used to estimate spray droplet-size data for different spray formulations through use of experimentally determined correction factors. Twelve spray-solution treatments were evaluated, ten of which contained a formulated glyphosate product and nine of these contained an additional tank-mix adjuvant. Droplet-size testing was conducted across multiple operational points (nozzle-orifice size, nozzle orientation spray pressure, and airspeed), in a high-speed wind tunnel, which corresponds to the response surface experimental model used to develop the present spray-nozzle models. The hypothesis that the different treatment solutions would respond linearly across a range of operational parameters and that a correction factor from relative to water plus non-ionic surfactant solution was proven false. When compared to water or the water plus non-ionic surfactant, the changes in atomization across the operation spectrum of the nozzle were not consistent and varied by formulation. Attempts to apply regression fits for a correction factor based on solution physical properties were not successful. With the formulated glyphosate tank mix used, none of the adjuvants tested, except the polymer, showed significant changes in droplet size under the high air shear regime. Whereas there is likely a need to develop formulated product-specific atomization models, the further addition of adjuvants do not significantly change the atomization characteristics and, as such, should not require a unique spray-nozzle model.
Rotary atomizer drop size distribution database
Wind tunnel measurements of drop Size distributions from Micronair A U4000 and A U5000 rotary atomizers were collected to develop a database for model use. The measurements varied tank mix, flow rate, air speed, and blade angle conditions, which were correlated by multiple regressions (average R-2 = 0.995 for A U4000 and 0.988 for AU5000). This database replaces an outdated set of rotary atomizer data measured in the 1980s by the USDA Forest Service and fills in a gap in data measured in the 1990s by the Spray Drift Task Force. Since current USDA Forest Service spray projects rely on rotary atomizers, the creation of the database (and its multiple regression interpolation) satisfies a need seen for ten years.
Temporal properties of secondary drop breakup in the bag breakup regime
Abstract The temporal properties of secondary drop breakup in the bag breakup regime were measured as a function of time for shock-wave-initiated disturbances in air at normal temperature and pressure. The test liquids included water, ethyl alcohol and various glycerol mixtures to yield liquid/gas density ratios of 633–893, Weber numbers of 13–20, Ohnesorge numbers of 0.0043–0.0427 and Reynolds numbers of 1550–2150. Single- and double-pulse shadowgraphy and holography were used to measure the structure, size and velocity of the parent drop, and the sizes and velocities of drops produced by secondary breakup. The parent drop undergoes significant deformation and lateral growth during breakup before forming a thin bag having a basal ring that is characteristic of the bag breakup regime. The basal ring contains roughly 56% of the initial drop volume (mass) and eventually yields drops having mean diameters of roughly 30% of the initial drop diameter by a Rayleigh breakup process; the size variations of drops formed from the basal ring increases with increasing Weber number due to the appearance of large ‘node’ drops that are characteristic of the onset of the multimode breakup regime. Breakup of the bag yields nearly monodisperse drops having diameters of roughly 4% of the initial drop diameter. The velocity distributions of the drops formed from breakup of the basal ring and the bag were individually independent of drop size but varied as a function of time and differed between the two groups. Many features of these phenomena were successfully correlated using phenomenological analyses. Finally, bag breakup requires considerable time (5–6 characteristic secondary drop breakup times) and extends over considerable streamwise distances (50–100 initial drop diameters) by the end of breakup, which suggests that bag breakup should be treated as a rate process, rather than by jump conditions, in some instances.