Measurement of hinge moments and model deformations in wind tunnels by means of Moir'e interferometry

Abstract

A non-intrusive Moire interferometry system has been designed to acquire the instantaneous deformation of models during wind tunnel testing. The resulting interferograms are evaluated without manual intervention using a technique based on the Fourier Transform. The deferomation of a large-scale model wing (generic model of a transport aircraft with a full span of 3.40 m) has been measured in the 8m x 6 m test section of the subsonic Deutsch- Niederlaendischer-Windkanal (DNW). At 400 individual locations along the span, the bending and twist deformation of the wing have been measured with an average accuracy of +- 0.1 mm and +-0.03, respectively. In a second experiment, the bending angle of a lap of a hypersonic vehicle was measured in order to determine the hinge moment due to aerodynamic loads. The experiment was carried out in the transonic wind tunnel Goettingen (TWG). To obtain data for comparison, the hinges were equipped with strain gauges. The results of both techniques show a maximum deviation of 0.02.