Background oriented Schlieren techniques for helicopter related large scale and flight testing

Abstract

Background Oriented Schlieren (BOS) methods suited for large-scale, in-flight testing are presented with special emphasis on the detection and tracing of blade tip vortices in situ. Feasibility and fidelity of reference-free BOS in conjunction with natural formation backgrounds and related evaluation methods are discussed, illustrating their simplicity and robustness. With image acquisition from a chaser aircraft the vortex field can be visualized for a wide range of flight attitudes, including complex maneuvers.