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Browsing by Issue Date, starting with "2013-01-05"

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  • Development of a New Dynamic Liquid Film Extension and Integration into a Spray Impingement Model
    Publication . Rodrigues, Christian; Barata, Jorge M M; Silva, André
    This 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.
    2013-01-05Journal article Embargoed access Show more
  • Numerical and Experimental Study of Two Impinging Jets in a Row through a Crossflow
    Publication . Vieira, Diana; Silva, André; Neves, Fernando M. S. P.; Carvalho, Pedro dos Santos Duarte; Barata, Jorge M M
    An experimental and numerical study is carried out to investigate the flowfield created by twin impinging jets aligned with a low velocity crossflow. The mean velocity, velocity fluctuation and visualization in the impingement region were obtained for a Reynolds number based on the jet exit conditions of Rej=4.3x104, an impingement height of 20.1 diameter and for a velocity ratios between the jet exit and the crossflow VR=Vj/Uo of 22.5, 33.7 and 43.8 with interject spacing, S of 6D. The experimental results show a large penetration of the first (upstream) impinging jet, giving rise to a ground vortex due to the collision of the radial wall jet and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) it is not so affected by the crossflow in terms of deflection, but it does not reach the ground due to the downstream wall jet that flows radially from the impinging point of the first jet along the ground. The results indicate a new flow pattern not yet reported so far, in which a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced negative pressures in the underside of the aircraft causing a pitching moment and a suction down force towards the ground. To extend the experimental results, the flow was also numerically simulated using a Reynolds Averaged Navier-Stokes formulation with the "k-ε" turbulence model.
    2013-01-05Journal article Embargoed access Show more