EFFECTS OF OSCILLATORY PLUNGING MOTION ON ROTARY WING BLADES | ||
| The International Conference on Applied Mechanics and Mechanical Engineering | ||
| Article 79, Volume 13, 13th International Conference on Applied Mechanics and Mechanical Engineering., May 2008, Pages 314-323 PDF (691.89 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/amme.2008.39393 | ||
| Author | ||
| ABOURAHMA A. A. | ||
| Ph. D Head of ARC Engineering Department. Cairo, Egypt. | ||
| Abstract | ||
| ABSTRACT The effect of blade oscillation on resulting air loads has promoted new interest in oscillatory blade aerodynamics. Rotary wings aerodynamics is considerably more complex than fixed wing aerodynamics. As an airfoil performs an oscillation, vortices are shed into the medium with a circulation strength equal in magnitude to the increase in circulation about the airfoil but opposite in direction. These disturbances are stored in the fluid because the shed vorticity convicts down stream at a local flow field velocity. The wake of the rotor consists of helical vortex sheet below the rotor b1ades. The wake remains near the rotor and therefore passes close to the following blades. The fundamental closed form solution of Theodorsen [1], and Lowey [2], provide the basis for theoretical work in this area. The closed form theory shows rapid changes in the lift deficiency function with changes in reduced frequency, wake spacing and frequency ratio. In the past, emphasis in the study of unsteady aerodynamics has tended to focus on flutter instability and the effect of unsteady aerodynamics on generating lift and torsional loads. The classic reference on this subject is that by Garrick [3]. While Garrick's work shows that an airfoil oscillating in pitch will typically produce drag in the lower reduced frequency range, k, it is found that the presence of another layer of shed vorticity of the proper phase can reduce the drag on plunging airfoils and depending upon wake spacing, reduced frequency and phase, may even enhance the propulsive force acting on the plunging airfoils. | ||
| Keywords | ||
| unsteady aerodynamics; Oscillatory Plunging Motion and rotary wing aerodynamics | ||
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