Control surface dynamics at transonic airspeeds

In a cooperative work JAXA and DLR performed two wind-tunnel experiments with a NLR7301 airfoil model performing harmonic pitch oscillations with a 25% trailing edge flap with individually controlled harmonic flap oscillations in the transonic airspeed regime. The unsteady flow field was measured with integrated pressure sensors. Nonlinear aerodynamic effects due to shock dynamics and unsteady flow separation were investigated as they are a key problem in flutter analysis of wings with control surfaces at transonic airspeeds. For highest accuracy of the data an optical position measurement system was used to measure the motion of the model and the flap and their deformation under wind load. It turned out that the deformation under wind load cannot be neglected, but has to be taken into account when comparing the data to numerical simulations. The target therefore is to derive a simple structural model for the deformation and to get corrected data at every point of the test envelope.