Stochastic modelling of turbulent spray dispersion in the near-field of orchard sprayers

Xu, Zhenlong; Walklate, P. J.; Rigby, S.G.; Richardson, G. Mark

doi:10.1016/s0167-6105(98)00026-9

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…Wilson & Shaw, 1977;Katul, 2004). The two equations k. model is the most popular in engineering applications and was used in several spray models (Weiner & Parkin, 1993;Zhu, Reichard, Fox, Brazee, & Ozkan, 1994;Xu et al, 1998;Brown & Sidhamed, 2001). In this work, the Reynolds averaged equations together with a k. model were used.…”

Section: Air Flow Modelmentioning

confidence: 99%

“…General CFD codes as CFX or Fluent (Fluent Inc., Lebanon, N.H.) describe the effect of turbulence dissipation by stochastic droplet tracking assuming that the air fluctuating velocities obey a Gaussian probability function (as described in Reichard, Zhu, Fox, & Brazee, 1992). Another method is to use random-walk models where the temporal fluctuation of the air velocity is determined by means of a Markov process (described for instance in Miller & Hadfield, 1989;Mokeba, Salt, Lee, & Ford, 1997or Xu et al, 1998. The AGDISP model is based on a spectral representation of the fluctuating velocity .…”

Section: Lagrangian Modelmentioning

confidence: 99%

“…Most models compute deposits as proportional to a "collection efficiency" (or "impaction efficiency" or "probability collection") which use and definition is variable but which always accounts for the inertial behaviour of the droplets and, in some cases, for the entrapment behaviour at the leaf level (Xu et al, 1998;Farooq & Salyani, 2004). The description of the expression of this coefficient will not be considered here.…”

Section: Impact Modelmentioning

confidence: 99%

“…They are based on a Lagrangian approach and use original ensemble-averaged turbulence equations avoiding the need of any random component. A Lagrangian approach coupled with stochastic droplet tracking was used for air assisted orchard sprayers by Xu, Walklate, Rigby, and Richardson (1998), and by Brown and Sidhamed (2001) as well who provided computations of the horizontal travel distances of droplets released from a forestry airblast sprayer for herbicide applications. In these Lagrangian approaches, only some trajectories were computed, usually one for each class of droplets diameter.…”

Section: Introductionmentioning

confidence: 99%

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A Lagrangian model for spray behaviour within vine canopies

Silva

Sinfort²,

Tinet³

et al. 2006

Journal of Aerosol Science

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This work concerns the numerical prediction of pesticide deposits on vine by air assisted sprayers. This numerical model consists in two different parts: the air flow characteristics were obtained through a Navier-Stokes solver in which additional terms have been introduced in order to account for the modification of the flow by the vine foliage. The theoretical form of these terms was derived through an averaging procedure. As a result, the canopy effect was modelled by introducing momentum and turbulence source terms in the Navier-Stokes equations. The constants were identified thanks to experimental data obtained by direct measurements of the air flow speeds through an artificial canopy. The second part of the model consists in simulating the droplet cloud by means of a lagrangian stochastic model. The average motion of the droplets was computed through the use of lagrangian coordinates and the turbulence effect on the droplets was interpreted in term of statistical properties of the droplet cloud. The tractor displacements were accounted for through unsteady boundary conditions. Once the size and the droplets cloud locations have been determined, the deposit was predicted for a vine row of one meter length using an efficiency coefficient obtained from simulations. Thanks to this approach we were able to quantify the effect of air turbulence on droplet deposition / Ce travail concerne la prédiction numérique de dépôts dans la vigne de pesticides pulvérisés avec assistance d'air. Le modèle numérique comprend deux parties : les caractétistiques du flux d'air sont obtenues à partir de la résolution des équations de Navier-Stokes dans lesquelles des termes additionnels ont été introduits pour prendre en compte les modifications du flux dues au feuillage. L'effet de la végétation est modélisé en introduisant des termes source de quantité de mouvement et de turbulence dans les équations de Navier Stokes. Les constantes ont été identifiées grâce à des données expérimentales obtenues par des mesures directes des vitesses d'air dans une végétation artificielle. la deuxième partie du modèle représente le nuage de goutteletters à l'aide d'une représentation Lagrangienne stochastique. Le mouvement moyen des gouttes est calculé à partir de leurs coordonnées Lagrangiennes et l'effet de la turbulence est pris en compte dans les propriétés statistiques du nuage; Les déplacements du tracteur sont pris en compte par des conditions aux limites transitoires. Une fois que la taille et la position du nuage de gouttelettes est déterminé, le dépot est calculé sur un mètre de rang de vigne en utilisant un coefficient d'efficacité calculé à l'aide de simulations. Grâce à cette approche, on peut prédire les effets de la turbulence sur le dépôt des goutte

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Section: Air Flow Modelmentioning

confidence: 99%

Section: Lagrangian Modelmentioning

confidence: 99%

Section: Impact Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Lagrangian model for spray behaviour within vine canopies

Silva

Sinfort²,

Tinet³

et al. 2006

Journal of Aerosol Science

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“…They allow the inclusion of several parameters that are extremely hard to control during field experiments, such as sprayer setup (García Ramos et al, 2015), weather conditions (Reichard, Zhu, Fox, Brazee, 1992) and vegetation structure (Endalew et al, 2009). Eulerian-Lagrangian CFD models have been developed to study the spray dispersion near the air-assisted sprayer (Xu, Walklate, Rigby, Richardson, 1998), the distance reached by droplets of a single nozzle (Zhu, Reichard, Fox, Brazee, Ozkan, 1994) and spray deposition on the leaves of grape vines (Da Silva, Sinfort, Tinet, Pierrat, Huberson, 2006) and pear trees (Endalew et al, 2010;Duga et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Eulerian–Lagrangian model of the behaviour of droplets produced by an air-assisted sprayer in a citrus orchard

Salcedo

Vallet

Granell

et al. 2017

Biosystems Engineering

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During pesticide applications to citrus trees using air-assisted (airblast) sprayers, only a proportion of the volume emitted reaches the vegetation and the rest is lost through drift, evaporation, etc. These losses can be hazardous for the environment. Knowing the characteristics of droplets within the turbulent currents around the canopy could improve the application efficiency. In a previous study, a 2D computational fluid dynamics (CFD) model was used to simulate the effect of a citrus canopy on the airflow from an airassisted sprayer was developed and validated. It considered the first element of the tree canopy as a solid body instead of a porous one. The aim of this study was to analyse the behaviour of the droplets for pesticide applications on citrus by means of an Eulerian-Lagrangian CFD model. It simulated both the air current from the sprayer fan and the wind and the behaviour of the droplets sprayed. Distance, height, velocity, Reynolds number, temperature, geometric and volumetric diameters at different times were obtained. With these parameters, new variables related to the kinetics and evaporation droplets were calculated. Simulation results estimated that 44% of the total sprayed volume reached the target tree, 28% reached adjacent trees, 20% was deposited on the ground and 8% was lost as atmospheric drift. The results largely matched an experimental mass balance carried out under similar conditions. The proposed model appears to be an appropriate tool for simulating treatments with air-assisted sprayers operating in citrus orchards.

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Dispersal of foliar plant pathogens: mechanisms, gradients and spatial patterns

McCartney

Fitt

The Epidemiology of Plant Diseases

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Stochastic modelling of turbulent spray dispersion in the near-field of orchard sprayers

Cited by 21 publications

References 8 publications

A Lagrangian model for spray behaviour within vine canopies

A Lagrangian model for spray behaviour within vine canopies

Eulerian–Lagrangian model of the behaviour of droplets produced by an air-assisted sprayer in a citrus orchard

Dispersal of foliar plant pathogens: mechanisms, gradients and spatial patterns

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