Numerical research on aerodynamic characteristics and flow fields of airfoil with serrated trailing edge

To research the aerodynamic characteristics and unsteady flow fields of NACA 0018 airfoil with or without serrated trailing edge based on large eddy simulation, the influences or rules were discussed by changing relative wave length and relative wave amplitude of trailing edge serrations. It was found that the effect of trailing edge serration parameters on aerodynamic performance of airfoil was a complex nonlinear process, lift-drag ratio increased at special angle of attack, the stall occured when the critical angle of attack of the bionic blade with trailing edge serrations was smaller. As an example, the lift-drag ratios of serrated trailing edge blades with different relative wave lengths were higher than original blade when angle of attack was between 9.4°and 14.8°, but there wasn’t a linear relationship between the lift-drag ratios and relative wave length.The findings showed that the trailing edge serrations could delay boundary layer separation of airfoil, promote wake flow mixing and energy diffusion, and change the structure of unsteady vortex and vortex shedding frequency. Changes of wave amplitude of trailing edge serrations influenced the unsteady flow characteristics more significantly. The turbulent jet and the counter-rotating vortices on suction surface occurred by the trailing edge serrations changed the circulation of the original blade, therefore aerodynamic characteristics and flow field of bionic blade with serrated trailing edge were influenced extremely.