| Summary: | A comprehensive study of the aerodynamic performance and wake development of aerofoils fitted with different types of trailing-edge serrations is provided. A symmetric NACA 0012 and a cambered NACA 65(12)-10 aerofoils have been studied experimentally. The aerodynamic force measurements have shown that the use of trailing-edge serrations can lead to significant reduction of the lift coefficient at low angles of attack for cambered aerofoils, while remaining negligible for symmetric aerofoils. The force measurements have also shown that the stall characteristics of the aerofoils do not change greatly as a result of the implementation of the trailing-edge serrations. The wake flow characteristics have been investigated using Particle Image Velocimetry (PIV), Laser Doppler Velocimetry (LDV) and hot-wire anemometer to improve the understanding of the wake development and the energy-frequency content of the wake turbulent structures associated with serrated trailing-edge. At relatively high angles of attack, where maximum lift-to-drag can be obtained, the turbulent kinetic energy and Reynolds stress results for the cambered aerofoils have shown that the wake flow turbulence can be greatly reduced in the aerofoil near wake region by using trailing-edge serrations, while that for the symmetric aerofoil were found to be less effective. The reduction of the wake turbulence for serrated cambered aerofoils is believed to be due to a complex interaction between the flow field over the tip and root planes and three-dimensional turbulent structures in the near-wake. The implementation of serrations has also shown a significant reduction of the wake flow energy over a wide range of frequencies. The reduction of turbulence within the near wake offers a new possibility in reducing noise generated by wake-aerofoil interaction. This will have significant implications for industrial applications involving multiple rows of aerofoils such as contra-rotating propellers, rotor-stator configuration, canard-wing body configuration, etc.
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