On the Near Wake Turbulent Flow Properties of the SD7003 Airfoil

摘要

Does the maximum aerodynamic efficiency condition correspond to reduced turbulent fluctuations in the near wake? Does approaching maximum aerodynamic efficiency effectuate onset of flow separation on the wing? This research is an endeavor to answer these fundamental questions and explore the relationship between near wake turbulent properties and aerodynamic efficiency. An SD7003 wall-to-wall model was chosen for this study. Time Resolved Particle Image Velocimetry (TR-PIV) was performed in the near wake of a wall-to-wall SD7003 wing for angles of attack (AoA) ranging from -2 to 8 degrees at AFRL's Horizontal Free-Surface Water Tunnel (HFWT). A detailed analysis of the near wake was performed to understand the trends between the mean (momentum deficit, vorticity, and two-point correlation) and fluctuating (U_(rms), V_(rms), Reynolds shear stress and? frequency spectrum) near wake flow quantities with aerodynamic efficiency. The results show evidence of three different wake signatures: 1) prior to the maximum aerodynamic efficiency with periodic vortex shedding, 2) in the vicinity of maximum aerodynamic efficiency with reduced magnitudes of mean and fluctuating velocity components in the wake and 3) beyond the maximum aerodynamic efficiency condition with an increase in the magnitudes of mean and fluctuating velocity components. The resulting correlations between the aerodynamic efficiency and the near wake properties could lead to better performance, attenuating unsteady aerodynamic loads, and even harvesting energy from the wake.