In order to enhance understanding of viscous-dominated blade flutter and to provide experimental data for validating unsteady viscous flow solutions, unsteady flow over a 2-D NACA-65 airfoil oscillating in torsion at an amplitude of 2° and a reduced frequency up to 0.69 has been experimentally investigated in a low-speed wind tunnel under different loading conditions. Unsteady pressure distribution is measured on both suction and pressure surfaces using pressure transducers. On the suction surface hot-film measurements are conducted to indicate the development of the unsteady boundary layer. Unsteady boundary layer behaviour and its effects on the airfoil’s aeroelasticity at the different loading conditions are demonstrated. The results also throw some light on understanding the onset mechanism of “dynamic stall” which involves a persistent convective pressure wave pattern with marked unstable aeroelastic characteristics.

This content is only available via PDF.