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- Modeling of Droplet Deformation and BreakupPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, A. R. R.The present paper addresses the macroscopic atomization characteristics of liquid-fuel droplets when subjected to the influence of a high velocity air crossflow. A breakup model is conceived by using a set of correlations available in the literature with the purpose of replicating such phenomena. The computational results are compared against experimental data to validate the model. The results show a reasonable agreement between measurements and predictions in both the qualitative and quantitative outcomes evaluated, which sustain the mathematical formulation adopted. However, further improvements may be aspired to, given the fact that there is a lack of experimental data available when shearing effects come into play in the mechanisms occurring during the atomization process. On the other hand, the use of two fuels (diesel and biodiesel) allowed to perception of a relevant impact of the liquid properties (particularly surface tension and viscosity) in the characteristics of the fragments resulting from the breakup event.
- Modeling of Evaporating Sprays Impinging onto Solid SurfacesPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, A. R. R.The present paper presents a numerical study on evaporating droplets impinging onto a solid surface through a crossflow. The characteristics of the initial spray are established by employing an empirical procedure that relies on a comprehensive set of free spray measurements. Distinct wall and crossflow temperatures are analyzed systematically to evaluate the influence of droplet evaporation on the final outcome of the simulation and, particularly, on the distribution of the thin liquid film that forms over the surface due to the deposition of incident droplets. The present computational model already has been proven to deliver accurate prediction results of the spray-wall interactions under different conditions. In this work, the conditions are extrapolated to a heated environment, which more adequately reproduces what is found in in-cylinder situations. The computational model is adapted to meet the new requirements and to perform within the range of conditions for which it is now being formulated. The analysis shows that higher temperatures lead to a decrease in the size of impinging droplets, an increase in the number of depositing droplets, a decrease in the fraction of mass of droplets contributing to the liquid film, and a more uniform distribution of the liquid layer over the surface.