Showing papers by "Julio Soria published in 2003"
TL;DR: In this paper, the three-dimensional structure of the flow behind a heaving and pitching finite-span wing is investigated using dye flow visualization at a Reynolds number of 164, which is a variation of the Strouhal number, pitch amplitude and heave/pitch phase angle.
Abstract: The three-dimensional structure of the flow behind a heaving and pitching finite-span wing is investigated using dye flow visualization at a Reynolds number of 164. Phase-locked image sequences, which are obtained from two orthogonal views, are combined to create a set of composite images that give an overall sense of the three-dimensional structure of the flow. A model of the vortex system behind the wing is constructed from the image sequences. Variations of the Strouhal number, pitch amplitude and heave/pitch phase angle are qualitatively shown to affect the structure of the wake.
183 citations
TL;DR: In this article, the multigrid cross-correlation digital PIV (MCCDPIV) technique is used to measure the flow field around a NACA 0015 airfoil at a 30° angle of attack when the flow is accelerated to a constant velocity from a quiescent state.
29 citations
29 Apr 2003
TL;DR: In this article, the structure of the vortical flow behind a symmetrical airfoil undergoing combinations of heave and pitch motions is investigated using qualitative dye flow visualization and the results suggest that the wake structures originating from the dynamic stall process are important for the analysis of these complex flows.
Abstract: The structure of the vortical flow behind a symmetrical airfoil of finite aspect ratio undergoing combinations of heave and pitch motions is investigated using qualitative dye flow visualization. The results are contrasted with flow visualizations obtained using electrolytic precipitation. The effect of changing the pitch amplitude is observed from the plan from view and wingtip view of the airfoil. With a Strouhal number of 0.35, Reyholds number based on airfoil chord of 164 and a phase angle of 90o, the maximum pitch amplitude is varied from 0° to 20°. The geometry of the downstream vortical flow is observed to change suggesting that the induced velocity from interacting structures decreases at lower pitch amplitudes. The rate of dynamic stall development may also be affected by variations in pitch amplitude since it appears that the timing of leading edge separation is affected. The flow field of an airfoil flapping periodically about a fixed axis appears to be influenced by the amplitude of pitching oscillations. At the tested Strouhal numbers the vortex formations appear to be primarily dependent on airfoil oscillation rather than heave translation. Furthermore, the results suggest that the wake structures originating from the dynamic stall process are important for the analysis of these complex flows. While the results from the two flow visualization techniques are similar, the dye flow visualization images provide greater qualitative insight. Inherently, precipitative techniques such as the one used here could provide good flow visualizations since the smoke/particles leave the surface of the airfoil, but the setup is found to be very sensitive to potential changes. The ion content in the electrolytic material was also found to play a role. Furthermore, the high ablation rate of the technique presented some practical problems.
8 citations