This study describes a novel measurement approach for combined flow and structural measurements in wind tunnels using robotic volumetric particle tracking velocimetry (PTV). The measurement approach is based on the application of a particle tracking algorithm on images including flow or structure tracers, where the latter are implemented by means of fiducial markers. The main steps of the measurement procedure comprise the simultaneous acquisition of flow and structure tracers in the same images, the distinction of the tracers leading to separate flow and structure image sets, the application of Lagrangian particle tracking and the further post-processing, and recombination of the obtained data. The approach is applied to the fluid-structure interaction between a flexible plate with a span of 1.2 m and a periodic gust. The total measurement volume amounts approximately to 150 liters. A phase-averaged description of the FSI problem is presented, with the focus on the effects of the spatio-temporal averaging of the flow information. The structural displacements obtained from the PTV system are validated against a scanning vibrometer. The phase-averaged displacement of the markers is also analyzed, assessing both the validity of the phase-averaged approach and the physical coherence of their motion with respect to a structural model of the plate. It is found that robotic volumetric PTV is suitable for the measurement of large-scale structural displacements, while it should not be used to measure small-scale vibrations. Finally, a visualization of the combined measurement is presented, together with an analysis of the consistency between the measured structure and flow field.

The aim of the paper is to experimentally validate a numerical design methodology for optimizing composite wings subject to gust and fatigue loading requirements and to assess the effect of fatigue on the aeroelastic performance of the wing. Traditionally, to account for fatigue in composite design, a knockdown factor on the maximum stress allowable is applied, resulting in a conservative design. In the current design methodology, an analytical fatigue model is used to reduce the conservativeness and exploit the potential of composite materials. To validate the proposed analytical model, a rectangular composite wing is designed and manufactured to be critical in strength, buckling and fatigue. An experimental campaign comprising wind tunnel and fatigue tests is performed. In the wind tunnel, both static and dynamic aeroelastic experiments are conducted to validate the numerical dynamic aeroelastic model. The fatigue test is used to validate the analytical fatigue model and to understand the effect of fatigue on aeroelastic properties of the wings. The results from experimental campaign validated both the aeroelastic predictions as well as fatigue predictions of the numerical design methodology. However the fatigue process resulted in degradation of the wing stiffness leading to change in the aeroelastic response of the wing.