Flexible DIC System for Wind Tunnel Testing of Lightweight Structures

Abstract

We propose an adjustable digital image correlation (DIC) system for the wind tunnel testing of small and large-scale aerospace and civil structures. A novel mounting rig with azimuth and pitch rotation fixtures was designed and developed for the DIC setup that can be installed from outside of the wind tunnel test section. The independent mounting rig makes the DIC system adjustable as per the shape and size of the test structure, which can reduce the installation and calibration efforts in wind tunnel testing. Telecentric lenses optimize the far-field optics of the DIC system. It allows the user to implement a rigorous calibration procedure to study magnification effects. We calibrated the DIC system at various fields of view and depths of field to ensure its suitability for wind tunnel experiments in which accuracy is a prime concern. The DIC measurements can be verified with the Euler transformation algorithm with a suitable combination of azimuth, pitch, and camera optical parameters. Case studies included a large-scale parachute model and a bioinspired flexible flapping wing to ensure the applicability of proposed system for both large- and small-scale structures. The inflated parachute diameter and the wing deformation fields were comparable to those predicted by the Euler transformation relationship. The DIC system can be coupled and synchronized with other measurement systems such as sting balances and particle image velocimetry for the real-time study of structural deformation, aerodynamic forces, and flow characteristics in the vicinity of structures.