Wavy Trailing Edge Effects on Truncated Thick Airfoil

Resumo

© 2023, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Thicker blunt trailing edge airfoils are extensively employed in many applications, especially in wind turbines. Their structural properties, such as strength section and area moment of inertia, and aerodynamic characteristics, such as higher curve slope and maximum lift coefficient, are particularly specials to design a blade that operates under varying cyclic loads and speeds, which establish dynamic conditions of creep loading, and fatigue stress. The main disadvantages are the higher drag and an intense and broadband noise, caused by the vortex shedding downstream. Many improvements have been achieved using passive flow controls to mitigate those problems, but there is still wide design space for better solutions. In this sense, the aim of this study is to investigate the potential of waviness applied on truncated trailing edge of thick airfoils as a possible efficient flow control mechanism. For this purpose, experiments in wind tunnel is carried out in order to understand the effects of different wavy geometries on truncated airfoil. A NACA 0020 airfoil is selected as a baseline profile, truncated at 15% from the trailing edge, and three configurations of waviness are tested: A = 0.11c, λ = 0.40c; A = 0.03c, λ = 0.40c; and A = 0.03c, λ = 0.11c. The phenomena is evaluated measuring forces in a wind tunnel at a Reynolds numbers of 200,000, and applying a technique of oil flow visualization. Main results shows that the wavy model presents much higher values of aerodynamic efficiency for lower angles of attack up to α = 5º. Besides that, another wavy configuration overcame the efficiency of the smooth truncated model for almost all pre and pos-stall regions. For low angles, a possible explanation is the break of vortex shedding coherence spanwise in the base, while for higher angles waviness allows to avoid flow separation over the surface.