Particle Image Velocimetry in Helicopter Aerodynamics: Developments, Challenges and Trends

New developments in measurement technology keep driving our experimental capabilities with regard to helicopter aerodynamics. The inherently unsteady nature of the helicopter flow field and the technical complexity of helicopter itself present a vast number of specific challenges to experimentalists. To illustrate the impact of the technological advancements on the way we study helicopter aerodynamics over the past two decades, we present some recent Particle Image Velocimetry (PIV) applications on blade tip vortices and dynamic stall, assessing the particular demands of studying rotary wing flows. We focus on time-resolved, tomographic and large-scale PIV applications. Furthermore, the combination of PIV with complementary measurement techniques like Background Oriented Schlieren method (BOS) is discussed and its potential contribution to a more detailed understanding of the underlying aerodynamics effects is outlined. Based on some foreseeable trends, finally, a glimpse into the future of PIV in helicopter aerodynamics is ventured.