Origin and Control of Unsteady Loading of Aerodynamic Surfaces Due to Vortex Breakdown and Stall
LEHIGH UNIV BETHLEHEM PA DEPT OF MECHANICAL ENGINEERING AND MECHANICS
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The occurrence of vortex breakdown on a swept wing at high angle-of-attack is a well-known phenomenon. It has important consequences for the unsteady loading of the wing surface, as well as the surface of an aerodynamic appendage, the most prevalent form being the tail of an aircraft. These types of vortex-surface interactions can be manipulated using simple control techniques. The first involves small-amplitude perturbations of either the wing or the aerodynamic surface. Another effective approach involves insertion of a wire in the vortex, whereby the wire is either transverse to, or in-line with, the axis of the vortex. All of the foregoing control techniques can significantly alter both the onset and structure of vortex breakdown. As a consequence, the unsteady loading that the vortex breakdown imposes upon the aerodynamic surface is altered as well. The major thrust of this research program has been determination of the source of the unsteadiness by use of cinema versions of high-image-density particle image velocimetry PIV, which generates space-time representations of the flow patterns. With this approach, it is possible to determine the underlying physics of the forcing functions for the unsteady loading. Furthermore, using this same experimental approach, it has been possible to determine the origin of loading in other configurations, which have links to aerodynamics.