Contributions of Particle Image Velocimetry to Helicopter Aerodynamics: A Review.

The advancement of flow measurement techniques continues to extend experimental boundaries and thus significantly contributes to improving our understanding of both basic and applied aerodynamics. This is particularly apparent in the case of particle image velocimetry (PIV), where its application has furthered the existing knowledge in several areas of helicopter rotor aerodynamics. The complex nature of helicopter rotor flows presents unique challenges to experimentalists, including transonic flow, concentrated vortices and dynamic stall. To illustrate the impact of the technological advancements on the way helicopter aerodynamics is studied today, the development of PIV since the early nineties of the last century is reviewed and some recent PIV applications are described. Using examples of main rotor wakes, dynamic stall and flow control investigations, the capabilities of large-scale, time-resolved and volumetric PIV are summarized.