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.
Development and validation of a 3D CFD model of drift and its application to air-assisted orchard sprayers.
Pesticides play an important role in providing high crop yields by minimising the risks associated with pests but some of the sprayed product may move beyond the intended target and result in drift. Modelling approaches can help understand the behaviour of spray drift using computer simulations. However, modelling drift from orchard spraying presents particular challenges: (1) the moving spray interacts with the canopy before drifting outside the target area; (2) the vertical wind profile in the orchard is different to neighbouring fields where there is different vegetation; (3) the moving air jet from the air-assistance cannot be ignored because the airspeed of the fan is usually higher than the wind speed. This work presents a three-dimensional (3D) computational fluid dynamics (CFD) model of spray drift from orchard sprayers that considers tree architecture, canopy wind flow and the movement of the sprayer to calculate sedimenting and airborne drift; thus tackling the challenges listed above. The model was validated against drift measurements from an apple orchard with different nozzles arrangements. The model was then used to evaluate the effect of drift reducing nozzles and fan airspeed on drift. The model predicted that drift reducing nozzles reduced the drifting distance by 50%, but increased near-tree ground deposition. This increase in ground deposition can be avoided whilst retaining the reduction in the drifting distance, by using a combination of drift reducing and standard nozzles. A reduced sprayer airflow can further reduce drift.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.