Browsing by Issue Date, starting with "2012-06-14"
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- Numerical Study of a Gas Turbine Engine Ground VortexPublication . Barata, Jorge M M; Maneta, Alexandre M.; Silva, AndréA computational method was used to predict and understand ground vortices forming between the ground and a 1/1th scale model intake of a engine. Calculations have been performed for the case of an irrotational crossflow mode of formation. Two different kinds of vortices appear around the intake: an inlet vortex and a trailing vortex. The computational method was found to describe all the main features of the flow for full scale geometry.
- Origins of Scientific Aircraft NavigationPublication . Barata, Jorge M M; Mendes, António; Morgado, Cândido M. P.; Neves, Fernando M. S. P.; Silva, AndréTwo Portuguese navigators crossed the South Atlantic in the beginning of the 20th century. They developed and used for the first time scientific methods of astronomic navigation when flying out of sight of land. A new model of sextant that could be used to measure the altitude of a star without the need of the sea horizon was developed. Another instrument called "path corrector" was introduced to calculate graphically the drift of an airplane and the direction of flight, taking into account the intensity and the direction of the winds. For the very first time in the history of the aviation the crossing of the South Atlantic had been achieved, and using an instrument that enabled an airplane's position to be precisely determined by astronomic navigation when flying out of sight of land.
- Experimental Study of Spray Dispersion and Wall InteractionPublication . Barata, Jorge M M; Silva, AndréThe present paper reports experimental results of a monosized droplet spray impinging on a surface through a crossflow that can be used to assist the development of computational models. Different impinging models are presented and the experimental results are used to provide a first insight into their adequacy to the description of the physical phenomena. The transition criteria between spray impingement regimes presently available revealed important difficulties to predict the corresponding threshold. Presently available numerical models to predict this type of flows require a careful evaluation of their applicability to the particular case.
- Experimental Study of a Ground Vortex: the Effect of the Crossflow VelocityPublication . Barata, Jorge M M; Bernardo, Nuno; Santos, Pedro José da Costa Teixeira; Silva, AndréLaser-Doppler measurements of the velocity characteristics of a ground vortex flow resulting from the collision of a wall jet with a boundary layer are presented and discussed together with flow visualization. In the present study velocity ratios between the boundary layer and the wall jet of 0.5 and 0.62 were considered. Two secondary vortices were found upstream the separation point for the highest velocity ratio. The angle of deflection of the upwash flow was found to decrease with the velocity ratio, while the wall jet penetration increases.