Review of measurement techniques for unsteady helicopter rotor flows

• Published in: Progress in aerospace sciences Vol. 111; p. 100566
• Main Authors: Gardner, A.D., Wolf, C.C., Raffel, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2019; Elsevier BV
• Subjects: Aerodynamics; BOS; Boundary layer transition; Differential thermal analysis; DIT; Dynamic stall; Fluid dynamics; Fluid flow; Helicopter rotors; Hot-film anemometry; Infrared analysis; Infrared detectors; Infrared imaging; IR thermography; Measurement techniques; Particle image velocimetry; PIV; Pressure sensors; Pressure transducer; PSP; Rotary wings; Thermography; TSP; Unsteady flow; Vortex; Hot-film anemometry; IR thermography; BOS; Helicopter rotors; Unsteady flow; PSP; DIT; TSP; 76-05; 2010 MSC: 76-02; Dynamic stall; Measurement techniques; Boundary layer transition; Pressure transducer; PIV; Vortex
• ISSN: 0376-0421; 1873-1724
• DOI: 10.1016/j.paerosci.2019.100566

The helicopter group at the DLR in Göttingen has been actively involved in the development of measurement techniques for unsteady flows, particularly as they apply to the problems found in unsteady rotor blade aerodynamics. This includes the development and validation of new techniques for the detection of dynamically moving boundary layer transition, and for the detection of dynamic stall and other transient flow separation events. These new techniques include pressure sensor analysis, differential infrared thermography, local infrared thermography and the automated analysis of hot-film data. Particle image velocimetry (PIV) and background oriented schlieren (BOS) have been used for the analysis of the unsteady off-body flow, and synchronised PIV-BOS-pressure measurements have allowed direct comparisons between different methods. The Lagrangian volumetric PIV variant, shake-the-box, has been used to analyse secondary vortex structures in the vortex wake. This review article will give an overview of the advances in that group, as well as placing their activities in the context of international advances in these areas.