Aviation

The understanding and identification of the physical instability mechanisms responsible for the appearance of unsteadiness and three-dimensionality on laminar separation bubbles can provide a fundamental insight into the aerodynamic characteristics of airfoils at stall conditions, and guide the development of strategies for the control of separated flows. Separation bubbles have been demonstrated to have an intrinsic instability mechanism, which results in the appearance of spanwise-periodic three-dimensional structures. The instability mechanism responsible for three-dimensionality was...

Several studies spanning since the 1970s to the present, considering turbulent flows at realistic conditions for aircraft flight, have amassed evidence on the dominance of a far-field tonal noise, usually associated with vortex-shedding from the trailing edge. Furthermore, the appearance of multiple tones has been documented for increasing values of the angle of attack and Mach number, which exhibit a ladder-like pattern in terms of the variation of the frequencies with increasing free-stream velocity. Different explanations have been suggested for the origin of the (i) single tone, (ii)...

Slat noise during aircraft landing is already a barrier to the development of quieter commercial airplanes. Investigations have been made by several research groups to understand the mechanism of slat noise generation. Most of the published works related to slat noise consider clean idealized geometries, whereas real slats contain some imperfections to enable its operation. The influence of a protrusion on the slat...

Laminar separation bubbles present a three-dimensional self-excited instability mechanism which leads to the appearance of spanwise-periodic structures. In incompressible flow, this mechanism was found to become active at conditions in which wave-like, two-dimensional perturbations are only convectively unstable. In the absence of continuous external excitation, the three-dimensional instability is expected to dominate the flow dynamics and initiate the laminar-turbulent transition. This work extends previous analyses by incorporating the effect of compressibility at subsonic...