Analysis of the impact of forced pitching oscillations in transonic flow on the transition onset and the aeroelastic behaviour of an airfoil

Within the European Clean Sky 2 Airframe ITD/NACOR project, a 2D airfoil laminar model was designed, manufactured, highly instrumented and tested in the Onera S2MA transonic wind tunnel in order to study the behaviour of the laminar-turbulent transition on the model under either steady angles of attack or forced dynamic pitch oscillations. The instrumentation included amongst others, static pressure taps, unsteady pressure sensors, accelerometers, optical displacement sensors and a high density hot films sensor array. The hot films were calibrated in order to get the time dependent wall shear stresses on the suction surface. Several key parameters were checked such as the inflow Mach number (from M=0.5 to M=0.77), the pitch angle (steady mean angle ranging from -3° to 3°, dynamic magnitude), the oscillation frequency and the Reynolds number. Steady and unsteady analysis pertaining to the influence of the different parameters are reported, including the pressure chordwise distributions with the inferred global loads and the transition locations. The comparisons between free laminar transition configurations and fully triggered turbulent flows are also given. Besides, several (U)RANS simulations performed with the Onera CFD code elsA using a transition model based on the AHD criteria and the Spalart-Allmaras turbulence model are shown.