Wake Development of Airfoils with Serrated Trailing Edges

Wake development and aero-acoustic performance of airfoils fitted with trailing-edge serrations have been studied experimentally. A symmetric (NACA 0012) and an asymmetric (NACA 65(12)-10) airfoil with different types of trailing-edge serrations have been tested over a wide range of angles of
attack and Reynolds number. The steady aerodynamic force measurements have shown that the use of trailing edge serrations leads to significant reduction of lift coefficient at low angles of attack. Particle Image Velocimetry (PIV), two-dimensional Laser Doppler Anemometry (LDA) and hot-wire
measurements were carried out in order to improve our understanding of the wake development and the energy content of the turbulent coherent structures. Significant reduction in the airfoils wake turbulence level has been observed, cause may include the interaction between the flow field over the tip and root planes and three dimensional horse-shoe and streamwise structures in the near wake. Results have also shown that the use of slotted sawtooth reduction can lead to significant reduction of turbulent kinetic energy and Reynold’s shear stress in the near wake region. The reduction of turbulence within the wake can significantly reduce the turbulence interaction noise in contra-rotating propellers, rotor-stator configurations, etc.