Christian Rodrigues

On the modelling of spray/wall impingement under crossflow conditions

Spray impingement is an important phenomenon affecting a wide variety of applications. In the present study, numerical simulations are carried out for predicting the outcome of such flows. An empirical procedure is used to define the initial spray characteristics, which relies on a comprehensive set of free spray measurements. The computer model is evaluated by comparing the numerical simulations against experiments on spray impacting on a solid surface with the presence of a crossflow. The predicted results show a reasonable agreement with the measurements. Moreover, further results are presented on the formation and evolution of the liquid film distribution over time.

Modeling of Droplet Deformation and Breakup

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 ...

Influence of the Energy Dissipation in the Spray Impingement Modeling

Simulating the complex dynamic phenomena that occur during the spray droplets impact is of great interest in numerous applications. In this sense, refine flexible dispersion models that can be adjusted through the use of adapted and more suitable empirical correlations in order to fit specific configurations with minimum time constraints would be a great asset both for industry and researchers. In this work, it is intended to study the dissipative energy term in the splash event. Besides the original relationship proposed in the dispersion model used, other equations of energy dissipation based on investigations devoted to the study of this parameter are introduced in the simulation and the results are tested against experimental data. Comparing all the relationships evaluated, the ones drawn from the literature deviates from what was expected. Therefore, it is evident that further research are essential in this field in order to propose a sub-model that could accurately define the energy dissipation term during the splash regime, whereas the investigations carried out so far only considered the energy loss through viscous dissipation during the spread regime.

Modeling of Evaporating Sprays Impinging onto Solid Surfaces

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 ...

On the Modelling of Evaporating Sprays Impinging onto Solid Surfaces

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, which relies on a comprehensive set of free spray measurements. Distinct wall and crossflow temperatures are analysed systematically to evaluate the influence of droplets evaporation on the final outcome of spray impingement, and, particularly, on the distribution of the thin liquid film over the surface. The present computational model already proved to deliver accurate predictions of the spray/wall interactions under different conditions. In this work, the conditions are extrapolated to a heated environment, which reproduce more adequately what is found in in-cylinder situations. The computational model is adapted to meet the new requirements and perform within the range of conditions for which it is now formulated. The analysis shows that higher temperatures lead to smaller impinging droplets, an increase in the number of depositing droplets but a decrease in the fraction of mass of particles contributing to the liquid film; and a more uniform distribution of the liquid layer over the surface.