Turbulent flow structure associated with vortex-induced fin buffeting

Selected results from an extensive experimental investigation showing the flowfield in the fin region of a deltacanard-configuration are presented. Results obtained include detailed flowfields of the time-dependent velocity components for various angles of attack (0-31.5 deg) at a test Reynolds number of 1.0 × 106 using hot-wire anemometry. The structure of the highly turbulent vortex dominated flow is clearly shown by time-averaged, root-mean-square (rms) and spectral distributions. Thus, strong interference effects between the canard and the wing vortex systems around the fin region are found. With increasing incidence the wing and the canard leading-edge vortices move inboard resulting in an increase of the velocity fluctuations in the area of the midsection. The power spectral density depicts significant frequency peaks related to the concentration of kinetic turbulent energy in the flow of the wing/canard vortex sheet. At high incidences the narrow-band turbulent energy induced by the vortex sheet affects the plane of symmetry because of the shift of the leading-edge vortex. This substantiates that fin oscillations at high-a are excited by narrow-band fluctuations due to vortical flow conditions.