Numerical investigation of the effects of dynamic camber variation on the airfoil characteristics of a pitching rotor airfoil

This paper presents a numerical investigation of a 2D harmonically morphed rotor airfoil during a pitching motion. Active camber morphing has the potential to significantly improve rotor efficiency when actuated dynamically during the pitching cycle over a rotor revolution. To analyze these potential performance gains, rotor comprehensive aeromechanics codes are frequently used. These analyses typically rely on steady airfoil tables as input. However, these two-dimensional aerodynamic input values do not account for the unsteady hysteresis and any aerodynamic interactions between the pitching motion and simultaneous dynamic camber morphing. To this end, URANS CFD simulations were conducted at a pitch frequency of f_θ =7 Hz that corresponds to the frequency of the pitching cycle of the Bo 105 main rotor. The simultaneous harmonic camber morphing of the aft section was actuated at the same frequency f_δ =7 Hz and was increased up to f_δ =14 Hz. The impact of the phase shift angle between the pitch and camber morphing actuation for different mean values and amplitudes of the camber morphing deflection were investigated and evaluated by means of the 2D aerodynamic characteristics C_n and C_m. Comparisons were made with steady airfoil coefficients obtained for the same operating conditions. Significant deviations were found between steady and unsteady airfoil characteristics. That is, the hysteresis loop of combined pitch and camber morphing contained significant unsteady effects. These effects are not included in standard steady airfoil lookup tables typically used for rotor comprehensive aeromechanics analysis.