An integrated optical system has been developed to enable simultaneous measurements of three-dimensional deformation and near-field tip vortex of flexible wings. The system combines a structured-light deformation measurement method and particle image velocimetry, operating at distinct wavelengths to avoid optical interference and achieving a fully non-intrusive measurement. Wind tunnel experiments are conducted on a simplified aircraft model equipped with one pair of rigid wings and two kinds of flexible wings at a Reynolds number of 1.1 × 105. The results show that increasing flexibility leads to larger three-dimensional deformations, with the wing tip moving upward, downstream, and spanwise inward. These deformations correlate closely with aerodynamic loading and induce corresponding vertical and spanwise displacements of the tip vortex. Despite the significant deformation as well as self-induced vibration, the radial circulation distribution of the tip vortex follows the self-similar law. Two kinds of vibration patterns, namely a bending vibration and a torsional vibration, are observed as associated with distinct patterns of vortex wandering. The bending vibration correlates with vertical wandering, and the torsional vibration enhances the spanwise wandering.
Guo et al. (Fri,) studied this question.