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- Development of a New Dynamic Liquid Film Extension and Integration into a Spray Impingement ModelPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, AndréThis paper is concerned with the improvement of macroscopic spray impingement simulations, for which a sub-model has been proposed for the formation of the liquid film over the impingement wall due to the deposition of particles. This computational extension deals with the interaction and spreading of the liquid between adjacent nodes due to the dynamic motion induced by the film inertia and crossflow velocity, as well as, the exchange of mass between incident drops, secondary droplets and liquid film. Moreover, an empirical correlation deduced from experimental data is used to define the relative liquid film thickness. Experimental data are used to validate the numerical model. Good agreement is obtained between numerical and experimental results for the test cases performed. The distribution of the relative liquid film thickness for two cases of crossflow velocities are also illustrated, as well as, its temporal evolution from start of injection. The dynamic behavior of the layer proved to be in concordance with the observations reported in experimental investigations available in the literature.
- On the modelling of spray/wall impingement under crossflow conditionsPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, AndréSpray 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 flim distribution over time.
- On the Modelling of Evaporating Sprays Impinging onto Solid SurfacesPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, AndréThe 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 in fluence of droplets evaporation on the nal outcome of spray impingement, and, particularly, on the distribution of the thin liquid lm 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.
- Influence of the Energy Dissipation in the Spray Impingement ModelingPublication . Rodrigues, Christian; Barata, Jorge M M; Silva, AndréSimulating 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.