ACCURACY OF COMBINED 3D SURFACE DEFORMATION MESUREMENT AND 3D POSITION TRACKING IN A WIND TUNNEL

Abstract

In this study the accuracy of a combined measurement of 3D surface deformation and the 3D position of an object in a wind tunnel is investigated. The aim of this study is the development of a system for the high accuracy measurement of an objects 3D position and deformation under wind load during simulated rapid maneuvers. In this situation, the 3D position and orientation of the model are considered to be unknown. The point tracking package PointTracker of the DaVis image processing software was used for the automatic detection of the 3D position and orientation of the model. The PointTracker calculates the 3D position from reflective markers placed on the model. The deformation is detected by the StrainMaster3D module of the DaVis software. In this software module a random structure on the model surface is used to calculate the 3D surface with a stereo camera setup. In a first experiment, the two measuring systems are compared by a combined measurement of marker positions and 3D surface from a random structure on a wing model. Deformations are simulated by small rotations of the wing in the wind tunnel. In a second experiment the position of an aircraft model with and without wind load and the deformation of the flaps were measured. The first experiment revealed that the results of the two measuring systems were consistent with an accuracy of about 20µm on a measuring area of 200 x 300 mm measuring deformations ranging from 0 mm to 1.7 mm. In the second experiment, a deformation of about 3.8 mm within the flaps was detected for changing wind load resulting form a change of the attack angle in the range of –10 degree to 10 degree (flaps angle 4 degree). With no wind load, the measured deformation was below 0.4 mm. As a result, the combination of the two measuring systems yields a ready to use system for the pure optical detection of the position, orientation and deformation of models in a wind tunnel with arbitrary movements or accelerations.