High-Speed PIV, deformation and BOS measurements for rotor aerodynamics

Abstract

Due to the complexity of the flow field around a helicopter, helicopter aerodynamics deal with quite a number of challenging aerodynamic problems like: flow separation on the retreating blades, compressible flow with shocks embedded on the advancing blades, a complex wake structure containing strong blade tip vortices, unsteady loads due to fluid structure interaction and many more. The extreme operation conditions on rotor blades limit the helicopter in many respects, like maximum speed, efficiency, noise emissions, loading capabilities and others. Due to the complex and frequently highly unsteady flow conditions at the rotor airfoils, experimental investigations are required to complete numerical simulations even if over the past decades, considerable progress has been made in the development of the performance prediction capabilities for isolated helicopter components. With modern CFD methods it is possible to compute the unsteady, three-dimensional flow field around a helicopter under moderate operation conditions (e.g. Antoniadisa et al. 2011). The computation time needed for such a computation with high spatial and temporal resolution is excessive and for now it remains unprofitable to incorporate CFD in the design iterations of future helicopters. Furthermore, CFD results still need validation and detailed experiments are needed to increase the physical understanding of helicopter flow phenomena and improve the modelling and prediction capabilities.