The aerodynamic study of the pitching NACA0012 airfoil with and without leading-edge tubercles at low Reynolds number

The aerodynamic characteristics of the sinusoidal pitching NACA0012 airfoil with and without the leading-edge tubercles at Reynolds number of 20000 and reduced frequency of 0.436 are investigated using water tunnel experiments and numerical simulations. Here the tubercle amplitude A=5 and 15% and wavelength λ=15 and 45% of the airfoil mean-chord are examined. The pitching amplitude and mean angle of attack are set to 30° and 0°, respectively. It is noticed that the maximum lift achieved by the baseline and all the leading-edge tubercle airfoils at the maximum angle of attack are the same in the considered A and λ range. However, we found the low-amplitude and wavelength tubercle airfoil has a superior half-pitching cycle mean lift, and the large amplitude and wavelength tubercle airfoil has a smaller complete pitching cycle mean drag than the baseline and other tubercle airfoils. Interestingly, the transition from drag to thrust is seen near the 0° angle of attack for the tubercle airfoils having large amplitude and wavelength. We have thoroughly characterised the flow features, including the counter-rotating vortex pairs and their effects on the leading-edge vortex for different tubercle wavelengths and amplitudes, explaining the aerodynamic behaviour of the tubercle airfoils.

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