Atomization modelling : An Eulerian approach
Résumé
Reducing pesticide drift requires particularly a better understanding of atomization process. An Eulerian model was therefore developed to model the atomization of a liquid sheet generated by a hollow cone nozzle. First, threedimensional calculations were performed to model the turbulent swirled flow inside the nozzle. Second, two-dimensional axisymmetric calculations were carried out to model liquid dispersion into the air and to calculate droplet Sauter Mean Diameter and droplet velocity. 3-D calculations were used as boundary conditions for the 2-D calculations. A “one-fluid-two-phase” approach was developed. A fluid with variable density was considered. The mean density was dependant on the Favre averaged liquid mass fraction. Liquid dispersion into air was calculated thanks to a transport equation for the mean liquid mass fraction. As the flow was highly anisotropic, the Reynolds Stress Model was used for turbulence. Moreover, a transport equation for the mean liquid/air surface area was developed. Production of the mean surface area was linked to the mean flow stretching, turbulence and droplet break up effect. Destruction of the mean surface area was related to droplet coalescence effect and took into account surface tension coefficient. Combining liquid mass fraction with surface area led indeed to the assessment of a Sauter Mean Diameter all over the calculation domain. The model was implemented in Fluent 6 Computational Fluid Dynamics software, using User Defined Functions. Experimental droplet axial velocity and droplet diameter were measured using Phase Doppler Anemometry. Comparisons between modeling and experimental data showed good agreement.
Domaines
Sciences de l'environnementOrigine | Fichiers produits par l'(les) auteur(s) |
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