Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- 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: Reynolds Number and Angle of Attack EffectsPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, A. R. R.Natural flight has always been the source of imagination for the Human being, but reproducing the propulsive systems used by animals is indeed complex. New challenges in today’s society have made biomimetics gain a lot of momentum because of the high performance and versatility these systems possess when subjected to the low Reynolds numbers effects. The main objective of the present work is the computational study of the influence of the number of Reynolds, angle of attack, frequency and amplitude of the oscillatory movement of a NACA0012 airfoil in the aerodynamic performance for a constant angle of attack over time. The thrust and power coefficients are obtained which together are used to calculate the propulsive efficiency. The simulations were performed using ANSYS Fluent with a RANS approach for Reynolds numbers between 8500 and 34000, reduced frequencies between 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the (constant over time) angle of attack was also studied in the range of 0º to 10º. The results indicate optimal operational conditions for the different Reynolds numbers and unprecedented results of the influence of the angle of attack on the aerodynamic coefficients and the propulsive efficiency is widely explored.
- Leading-Edge Parametric Study of the NACA0012-IK30 AirfoilPublication . Camacho, Emanuel; Marques, Flávio D.; Silva, A. R. R.; Barata, Jorge M MIn many research areas, such as rotor dynamics and biomimetics, the dynamics of oscillating airfoils are of great interest. The findings of this study provide great insight into the importance of the leading edge regarding the propulsive characteristics of flapping airfoils. The main objective of the present work is to analyze the influence of the leading-edge pitching amplitude of the NACA0012-IK30 airfoil at a Reynolds number of 1.4x10^4, constant Strouhal number of 0.15 with three different (k,h) combinations and five leading-edge pitching amplitudes (A_alpha=0º,5º,10º,15º,20º). Using a RANS approach with the turbulence model k-omega SST coupled with the Intermittency Transition Model, results show that changing the leading-edge pitching amplitude has great impact on thrust enhancement, although presenting a small influence when it comes to lower nondimensional amplitudes. The required power coefficient is typically reduced while increasing the leading-edge pitching amplitude which, in some cases, provides an increase up to 211% in propulsive efficiency.
- 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.
- Wing Design and Analysis for Micro Air Vehicle DevelopmentPublication . Ferreira, Rúben; Camacho, Emanuel; Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréNatural flight was always a source of inspiration to human beings, and by observing it, new technologies emerged, especially in bioinspired aerial vehicle design. The main objective of the present work is to experimentally evaluate the influence of the wing shape on their behavior and power consumption. To accomplish that goal, four wings were selected and an experimental rig was developed. Airflow velocities tested ranged from 0 up to 4 m s−1 with four different throttle positions. Flapping frequency and amplitude were obtained from high-speed camera tests and the power consumption of the wings tested was measured. It is observed that amplitude is between 0.12 m and 0.25 m, frequency between 4 and 15 Hz. Regarding power consumption, the design wings presented lower averaged power-to-weight ratio values when compared to BionicBird wings.