Experimental Study of a Plunging NACA0012 Airfoil under Asymmetric Oscillations

• Autor(a) principal: Silva, Joana Gomes Santos
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/13764
• topic: Biomimética; Cinemática Assimétrica; Perfil Oscilante; Vór- Tices de Bordo de Fuga; Vórtices de Bordo de Ataque; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

The need to overcome new challenges made the human being seek in nature ways to surpass specific problems through Biomimetics. Through the observation of locomotion modes of animals such as birds and insects, a great interest emerged in this form of motion that allows the simultaneous generation of thrust and lift at low Reynolds numbers. This dissertation has the primary objective of exploring experimentally the asymmetric movement of a NACA0012 airfoil in purely vertical motion. It is also intended to study the influence of the nondimensional amplitude and reduced frequency on the wake patterns of the airfoil. Finally, will be performed an analysis of the influence of motion asymmetry, nondimensional amplitude and reduced frequency on the airfoil’s effective angle of attack. The tests are carried out in an open-section wind tunnel using a smoke machine to mark the flow and a highspeed camera to capture the airfoil’s wake. All tests are performed with a Reynolds number of 1 × 104 and four levels of asymmetry, ? = 0.5, ? = 0.6, ? = 0.7 and ? = 0.8, are considered. The nondimensional amplitude studied is between 0.125 and 0.5, and the reduced frequency ranges between 0.5 and 8. The visualization of the flow indicates that the asymmetric motion produces both thrust and lift and that increasing the asymmetry parameter makes the vorticity more intense. Furthermore, these vortices form earlier. Nondimensional amplitude and reduced frequency have a similar impact. It is found that vortices form further upstream with the increase of these parameters, and their intensity also increases. Regarding the effective angle of attack, it is observed through the results that the rise of these three parameters causes an increase in this angle. The separation of the flow occurs earlier for higher values of the asymmetry parameter, nondimensional amplitude and reduced frequency.