Aeroelastic Wing Performance in High-Intensity Freestream Turbulence: Integral Length Scale Effects

The impact of variations in the integral length scale of incoming freestream turbulence on an aeroelastic NACA0012 wing is investigated using force, moment, and particle image velocimetry measurements. At a chord-based Reynolds number (Re=U infinity c/nu) of 2 & sdot;105, an active grid generates turbulence intensities of 15% at normalized integral length scales ranging from 0.5c to 1c (where c is the chord length). The introduction of turbulence improves the time-averaged performance characteristics of the aeroelastic wing by delaying stall and increasing the peak lift coefficient. The turbulence excites structural modes such as bending and torsion, but it does not introduce new frequencies in the forces and moments. Instead, it amplifies particular frequencies that appear in the clean flow case. It is observed that, for full-chord integral length scales, the magnitude of the fluctuations in forces and moments at the frequency of a structural bending mode is excited. Meanwhile, at half-chord integral length scales, the magnitude of the fluctuations in forces and moments at the frequency of a torsional response is excited. The structural excitations resulting from the incoming turbulence in turn generate unique characteristics in the flowfield surrounding the aeroelastic wing.