Unsteady Separated Flows: Vorticity and Turbulence.
COLORADO UNIV AT BOULDER DEPT OF AEROSPACE ENGINEERING SCIENCES
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Throughout a wide combination of initial pitch angles, pitch amplitudes and pitch rates, for an NACA 0015 airfoil section, several unsteady flow initiation and development trends have been documented. The effects of mean angle of attack and reduced frequency, and the interactions between them, are generally linear for the ranges studied. Incremental changes in reduced frequency and mean pitch angle resulted in later or earlier vortex initiation, respectively, within the pitch cycle. Other notable features of the flowfield development include the initiation of a prominent trailing edge vortex as the leading edge vortex sheds, and the convection velocity of the leading edge vortex. Similar tests employing a flat plate produced somewhat different results. The vortices were more coherent and convected at higher velocities. In general, however, the developmental trends across the parameters tested followed those of the airfoil model. Keywords Unsteady flows Separated flows Dynamic stall Vortex shedding.
- Fluid Mechanics