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- 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, AndréThe study of the complex flowfield produced by a single jet impinging on a wall through a crossflow has been carried out over the past several decades with many different motivations and applications. This type of flow is most relevant to the successful design and operation of vertical and/or short take-off and landing aircrafts. The increased momentum of the wall jet is consistent with the movement of the separation point in the X direction, but the region of higher mean vertical velocity spreads in the wall direction. Nevertheless, their results did not exhibit any bimodal LDV histograms of discrete frequencies that could be associated with any instabilities or oscillations. To avoid the influence of the impinging region, a plane wall jet is produced independently. The wall jet collides with the boundary layer produced using a conventional wind tunnel giving rise to a highly curved region, which can be studied for different velocity ratios between the wall jet and crossflow.
- Experimental Study of a Ground VortexPublication . Barata, Jorge M M; Ribeiro, Samuel; Santos, Pedro José da Costa Teixeira; Silva, AndréLaser-Doppler measurements of the mean and turbulent components of the velocity flowfield resulting from the frontal collision of a wall jet with a boundary layer are presented and discussed, together with the visualization of the flow with direct photography and digital film imaging. The experiments were carried out for boundary-layer-to-wall- jet velocity ratios of 0.5 and 0.58. The results revealed the existence of a small counter-rotating recirculating zone located upstream (in the sense of the wall-jet flow) of the separation point, not reported before for this type of flow. This secondary vortex has an oscillating behavior observed in other ground-vortex flows, similar to that which can be observed, namely, through the bimodal histogram of the horizontal velocity (parallel to the wall) measurements, although the power spectra measurements do not exhibit any particular peaks.
- 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.