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- Effects of a Dynamic Leading Edge on a Plunging AirfoilPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Marques, Flávio D.; Barata, Jorge M M; Silva, AndréThe dynamics of oscillating airfoils are of great interest in many research areas such as rotor dynamics and biomimetics. The results reported in this research provide an insight into the mechanics of birds’ leading edge and how the dynamic curvature of the airfoil can highly benefit the aerodynamic and propulsive performance, especially at high angles of attack. The main goal of the current work is to numerically investigate the influence of a deflecting leading edge on the propulsive coefficients and flowfield created by a plunging airfoil at a Reynolds number of 1.4 × 104 and a constant Strouhal number of 0.15 with different ( k, ℎ) combinations. Employing a RANS approach with the proposed NACA0012-IK30 airfoil, results show that dynamically deflecting the leading edge significantly improves the propulsive efficiency of the airfoil by either reducing the required power or improving the thrust production. The outcomes regarding the propulsive efficiency show a considerable increase of up to 92% when the higher nondimensional amplitude was considered.
- Plunging Airfoil Motion: Effects of Unequal Ascending and Descending VelocitiesPublication . Rodrigues, Diana Carvalho; Camacho, Emanuel; Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, A. R. R.Biomimetics is a multidisciplinary area of science studying the development of new technologies, whose source of inspiration is Nature and has given rise to new technologies inspired by biological solutions at macro and nanoscales. Successive work carried out by researchers in this field revealed that flapping wings offers not only benefits but unique aerodynamic advantages when compared to the traditional fixed-wings, especially when approaching small scales. This work presents an experimental study concerning the created vortical structures of a plunging NACA0012 airfoil subjected to an asymmetrical motion at a Reynolds number of 1500 with different reduced frequencies and nondimensional amplitudes. The asymmetric motion studied was based on a velocity triangular wave with special focus in a plunging cycle asymmetry of 75%. Over its plunging motion, the unequal ascending and descending velocities revealed that the airfoil can produce both thrust and lift simultaneously. Leading-Edge Vortex (LEV) formation and its convection over the upper surface of the airfoil was seen as a possible power reduction mechanism which could be a way to improve propulsive and energy extraction efficiencies.