Impulsive Flow Attachment Process over a NACA 0015 under the Action of Fluidic Vortex Generators (FVG)

TitleImpulsive Flow Attachment Process over a NACA 0015 under the Action of Fluidic Vortex Generators (FVG)
Publication TypeConference Paper
Year of Publication2009
AuthorsSiauw, W. Long, J-P. Bonnet, J. Tensi, L. Cordier, B. Noack, and L. Cattafesta
Conference NameSixth International Symposium on Turbulence and Shear Flow Phenomenon
Date PublishedJune
Conference LocationSeoul, South Korea

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 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.