Aerodynamic characteristics of variable-camber airfoil/rotor in forward flight

The development of smart materials has made it possible to achieve continuous variable-camber function of airfoil/rotor. To study the influence mechanism of continuous variable-camber airfoil/rotor on the strong unsteady aerodynamic characteristics during dynamic stall, a rotor flowfield simulation method is established based on the moving-embedded mesh method and URANS equation, and the body-fitted mesh of variable-camber airfoil/rotor is reconstructed by the RBF mesh deformation method. The effectiveness of the mesh method and the numerical simulation method is verified by comparing the unsteady aerodynamic characteristics of the NACA0012 airfoil, the SA349/2 rotor and the SMART rotor with trailing edge winglet. A comparison with the traditional rigid trailing edge winglet reveal the principle and advantage of continuous variable-camber technology for improving the average lift-to-drag ratio of airfoil. The complex effect of variable-camber airfoil/rotor on dynamic stall characteristics is captured, and the influences of motion frequency, amplitude and initial phase of the variable-camber on the unsteady aerodynamic characteristics of the airfoil, as well as the unsteady aerodynamic load variation characteristics of the three-dimensional rotating blade with different azimuth angles and blade sections, are fully considered. The results demonstrate that the continuous variable-camber technology can effectively control the aerodynamic performance of the rotor through collaborative allocation of variable-camber frequencies. An approximate linear relationship between the variable-camber amplitude and the unsteady aerodynamic increment of the airfoil/rotor is observed even under the condition of dynamic stall. The initial phase of variable-camber should be consistent with the cyclic pitch control of rotor to suppress the divergence of sectional aerodynamic coefficient. The above rules indicate that the continuous variable-camber technology has great potential in rotor trim or vibration reduction.