Self-Excited Vibration of a Leading-Edge Flap on a Stalled Airfoil

This study numerically investigates the effect of a flexible covert-inspired leading-edge flap on the aerodynamic characteristics of a stalled airfoil. The self-excited oscillations of the flap attached at the leading edge of the aerofoil that underline the flow separation characteristics are of primary interest to this study. A finite volume method-based code, OpenFOAM, and a finite element method-based code, Calculix, are used to solve the governing equations for the fluid and solid counterparts, respectively. The fluid and solid solvers are coupled using the open-source coupling library, preCICE, through a partitioned approach. A parallel implicit coupling scheme with Interface Quasi-Newton Inverse Least Squares (IQN-ILS) acceleration scheme was used to ensure a strong fluid-solid coupling. Present findings demonstrate that the self-excited vibrations of the flexible flaps attached to an airfoil surface can delay stall and enhance lift generation. High lift is obtained when the leading-edge flap vibration gets locked in with the near-field wake in a narrow frequency band. To this end, the dimensionless bending rigidity, mass ratio, and the initial angle of the flap strongly influence the aerodynamic performance. The findings of this study may be useful for the novel bio-mimetic design of micro-aerial vehicles.