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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

TRANSIENT DYNAMICS OF THE FLOW AROUND A NACA 0015 AIRFOIL USING FLUIDIC VORTEX GENERATORS

pages 879-884
DOI: 10.1615/TSFP6.1410
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Краткое описание

The unsteady activation/deactivation of fluidic vortex generators on a NACA 0015 airfoil is studied to understand the transient dynamics of flow separation control. The Reynolds number is high enough and the boundary layer is tripped, so the boundary layer is fully turbulent. Conditional PIV of the airfoil wake is obtained phase-locked to the actuator trigger signal, allowing reconstruction of the transient processes. When the flow is impulsively attached, the velocity field in the near wake exhibit a complex transient behavior associated with the formation and shedding of a starting vortex. This confirms results in the literature obtained in comparable configurations. The separation dynamics when actuation is stopped is a more gradual process. The Proper Orthogonal Decomposition reveals low-dimensional transient dynamics, with 98% of the fluctuation energy captured by the first four modes. The behavior is quantitatively well captured by a 4-dimensional dynamical system with the corresponding mode amplitudes. Analysis accurately determines typical time scales for attachment and separation processes are T+ = ΔtU/Lsep = 10 and 20 in conventional non dimensional values. This study adds to experimental investigations of this scale with essential insights for the targeted closed-loop control.

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