Deducing Aerodynamic Mechanisms from Near- and Far-Wake Measurements of Fixed and Flapping Wings at Moderate Reynolds Number (Invited)

‡Biologists and engineers would like to understand more about the aerodynamics of flapping wing flight, because it’s there, and because there could be reasons for emulating it in engineering designs. The geometry and kinematics of real wings operated by live, untethered animals are famously complicated. This paper describes a research program that has two complementary approaches. The first is to make quantitative descriptions of the air flows behind birds in steady flight in a wind tunnel, with the aim of making deductions or inferences about the wing and body aerodynamics based on the free wake signature. The second approach is to simplify the problem as much as possible, and look in detail at the air flow around fixed wing shapes at the appropriate Reynolds number. Even such ostensibly simple problems have flow solutions of great complexity, but have the advantage that crosschecks can be made between directly measured and wake-measured force components. Recent progress in both fields is summarized, and further practical research problems of interest to both communities are noted.