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Vorticity Dynamics and Control of Dynamic Stall.
Final rept. 15 Apr 92-14 Jun 94,
NIELSEN ENGINEERING AND RESEARCH INC MOUNTAIN VIEW CA
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The goal of the research was to understand key issues of vorticity dynamics prior to, during, and after the initiation of dynamic stall. The first portion of this work examined the of indicial theory to the predIction of dynamic applicability stall. The research focused on extending the semi-analytical formalism of indicial theory to predict the vorticity fluxes and the vorticity accumulation at the leading edge during unsteady maneuver. In the second portion of this work, highly accurate two-dimensional solutions of the Navier-Stokes equations were used on a model problem to investigate the Reynolds number scaling of incipient flow separation between Re 50,000 and Re 800,000. This portion of the work was motivated by the suggestion that the appearance of eruptive plumes of vorticity at high Reynolds number might be critical to the formation of the dynamic stall vortex. The results of the research appear to contradict the hypothesis that a form of Reynolds number bifurcation must take place at some intermediate laminar Reynolds number. Instead, sell- similar behavior was observed, at least up to the time of formation of the primary stall vortex.
APPROVED FOR PUBLIC RELEASE