Three-dimensional flow and load characteristics of flexible revolving wings at low Reynolds number

Increasing interest in the field of micro air vehicles has stimulated research activities regarding biological flapping-wing flight. An important characteristic of biological flapping-wing flight that is not commonly taken into account in mechanical model simulations is the influence of wing flexibility. This experimental study explores the flow field and fluid-dynamic loads generated by revolving low-aspect-ratio wings with different degree of chordwise flexibility at a Reynolds number of 10,000. The experimental campaign consisted of phase-locked tomographic particle image velocimetry (PIV) measurements complemented with simultaneous force measurements. The three-dimensional velocity fields are captured in three measurement volumes positioned side-by-side along the span of the wing for different phases of the revolving motion, generating a time-resolved volumetric velocity field data set. Subsequently, from the velocity data the pressure fields are reconstructed as well as the loads acting on the wing. In this study the link between the temporal evolution of the vortical structures and the associated pressure forces acting on the wing is investigated in detail.Aerospace EngineeringAerodynamics, Wind Energy & Propulsio