An optical position monitoring system for investigation of model displacement and transient motion of wind tunnel models

Abstract

In complex wind tunnel test simulating unsteady manoeuvres, e.g. transient rolling motion at large angles of attack, it is necessary to determine the actual position of the wind tunnel model, since existing measuring techniques could not give reliable data of the position of the wind tunnel model, e.g. angle of attack, rolling angle. To solve the described problem an optical system has been developed which basically focuses the model, or part of it, onto an image plane where a line sensor is placed, utilising four independent line CCD sensors with a data rate of 6.4 kHz. To evaluate the data from the line sensors digital image processing is used to transform the data from the sensor frame of reference to the wind tunnel co-ordinate system leading to the actual model position within the wind tunnel frame of reference. In the presented experiment the displacement and motion of a rolling delta wing model in the DNW-TWG has been investigated. The position of a delta wing has been determined by means of the newly developed optical position monitoring system of DLR. The investigations have been performed in the 1 m x 1 m test section of the DNW-TWG wind tunnel. The wind tunnel was operated at Mach numbers up to 0.85. The model has a sweep angle L= 65° and a length of 433 mm, the maximum corresponding Reynolds number based on the model length in the present experiment is 8.5*106. The angle of incidence has been varied between 9° and 25°. The largest applied rolling rate was w=3200 °/s. A typical model rolling motion in an interval between 0° and 90° leads to 72 position data for w=3200 °/s.