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Browsing by Author "Rodrigues, Diana Carvalho"

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  • Effect of Reynolds Number on a Plunging Airfoil
    Publication . Rodrigues, Diana Carvalho; Camacho, E. A. R.; Neves, Fernando M. S. P.; Silva, André; Barata, Jorge M M
    Biomimetics is an area of science that studies the development of new technologies, whose source of inspiration is Nature. Unlike traditional aircraft, animals only have one structure to create both lift and thrust, and for Humans, although in the recent years the studies in this area increased, a long way must be made to achieve their capability. The present paper focuses on the effect of the Reynolds number on the wake configuration produced by a plunging airfoil. The experimental work was performed using an airstream, that was marked with smoke, with an oscillating airfoil NACA0012, whose dimensions are 44cm and 10cm of span and aerodynamic chord, respectively. The motion prescribed for the wing is harmonic, since it very well represents the type of motion seen in Nature. Frequency and amplitude were maintained, respectively, at 1.2Hz and 2.8cm, and the wind speed range from 0.25m/s to 1.00m/s, which represents a nondimensional amplitude of 0.28, a reduced frequencies of 3.02, 1.51 and 0.75, and a Strouhal number and a Reynolds number range of, 0.07 – 0.27 and 1,500 – 6,300, respectively. Results indicate that, with the increase of the Reynolds number, the convection effects become more predominant than diffusion effects, the curvature of the wakes and the maximum effective angle of attack decrease, and time and configuration of vortex shedding change. For Re = 1,500, St = 0.27, another relevant conclusion appears; the interaction of the leading-edge vortex with the trailing-edge vortex indicates an improvement of the aerodynamic performance of this system.
    2020-06-02Journal article Open access Show more
  • Plunging Airfoil Motion: Effects of Unequal Ascending and Descending Velocities
    Publication . 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.
    2020-06-08Conference object Restricted access Show more
  • Visulização e análise das estruturas na esteira de um perfil NACA0012 em movimento oscilatório vertical
    Publication . Rodrigues, Diana Carvalho; Silva, André Resende Rodrigues da
    A biomimética é uma área da ciência que se dedica ao estudo da natureza, tendo por base a sua imitação. Os perfis oscilantes, na natureza, apresentam um alto desempenho propulsivo e, por isso, o ser humano tem desenvolvido um grande interesse nos estudos sobre estas temáticas. Desta forma, este trabalho, no âmbito dos perfis oscilantes, teve por base a visualização, bidimensional, das esteiras libertadas por um perfil NACA0012 sujeito a um movimento puramente vertical, periódico, não sinusoidal, simétrico e assimétrico, a diferentes combinações de velocidade, amplitude e frequência. Os resultados permitiram concluir que o surgimento de VBAs, assim como o tipo de esteira libertada por um perfil oscilante, dependem essencialmente dos parâmetros h e k. Contudo, a influência de cada parâmetro nunca é independente, sendo que os parâmetros apenas ditam a tendência do tipo de estruturas libertadas pelo perfil, mas, de forma isolada, não são capazes de afirmar essa mesma tendência.
    2020-07-27Master thesis Open access Show more