| Summary: | 博士 === 國立臺灣科技大學 === 機械工程系 === 90 === Abstract
The surface-flow characteristics and aerodynamic performance of a cantilever wing model subjected to the influence of a leading-edge control rod are studied in a wind tunnel. Circular rods of various materials and diameters installed at various distances from leading edge of the wing are tested at low chord Reynolds numbers. Some selected small-diameter rods present a self-excited transverse vibration when they are placed very close to the leading edge. Through the surface oil-flow technique, the natural wing displays complex surface flow patterns, which are commonly observed at Reynolds number range of 104~106. Under the action of rod vibration, the turbulent boundary-layer behaviors, usually found on a wing surface at large Reynolds numbers, are observed. The separation resistance of boundary layer of the vibrating-rod controlled wing is remarkably larger than the natural and rod-wake disturbed wings. Transverse vibration of the elastic rod induces large oscillation in the surface flows and remarkably retards angle-of-attack of the boundary layer separation from the leading edge. The oscillation intensity in the surface flows of the case of vibrating rod may attain as high as 70%, while the fluctuation intensity in the rod-wake disturbed surface flows is about the level of 20 to 40%. Measurements of aerodynamic loads using a PC-based force/moment sensing system show that the stall angle can be postponed by around 80%, the maximum lift-coefficient can be increased by about 20%, and the lift/drag ratio may be increased by approximately 50% at large angles of attack. The improvements of lift and stall angle-of-attack are closely related to the modulation of surface flow, which is caused by the vibration-induced transverse velocity fluctuations superimposed on the boundary layer. Details of the influences are discussed and illustrated.
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