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

ifasd2024 Tracking Number 67

The development and the validation of the numerical prediction tools for the aeroelastic behaviour of laminar wings goes first through the assessment and the potential updating of these tools on models undergoing forced harmonic motions. This implies the availability of an extended enough data base. Within the European Clean Sky 2 Airframe ITD/NACOR project, a 2D model equipped with a laminar airfoil was thus designed, manufactured, highly instrumented and implemented in the Onera S2MA wind tunnel in order to study the behaviour of the laminar-turbulent transition on the model under forced dynamic pitch oscillations, mainly in transonic flow conditions. The instrumentation includes amongst others, static pressure taps, unsteady pressure sensors, accelerometers, optical displacement sensors and a high density hot films sensor array. Several parameters were checked such as the inflow Mach number, the pitch angle (steady mean angle ranging from -3° to 3°, dynamic magnitude), the oscillation frequency and the Reynolds number. The processing of the different time signals coming from steady and unsteady test configurations give an understanding of the effect of the above parameters on steady and unsteady aerodynamics and on the transition chordwise motion peculiarities. The corresponding numerical simulations are performed using the Onera CFD code elsA with different turbulence and transition models (Arnal-Habiballah-Delcourt (AHD) criterion, Menter-Langtry,…). These simulations yield not only the variation of both steady and unsteady aerodynamic global forces and pressure chordwise distributions but also the steady and unsteady transition locations towards the pitch angle. Experimental and numerical comparisons, relating to free transition and triggered turbulent flow, are also presented as they bring some clues on the most appropriate turbulent model and transition criterion to be used in simulations and provide some additional insight on the impact of laminarity on the overall steady and unsteady performances of such airfoils.