Numerical Study of Owls' Leading-Edge Serrations

Nocturnal owls’ species fly almost silently. Their stealth flight is commonly attributed to a combination of their wings’ special microfeatures and kinematics. These features are distributed over the wingspan in both the leading and trailing edge regions as well as over the planform. One of these microfeatures is known as leading-edge serrations. They are rigid, comb-like structures located at the primary feathers. Their length is about 1% of the wing chord and they are aligned at an angle in respect to the incoming flow, positioned in a ‘hooks-like’ formation over the leading-edge surface. In this study, we investigate the flow characteristics over a Barn owl (Tyto alba) wing section with and without leading-edge serrations geometry at an intermediate chord-based Reynolds number (Re_c ~ 40,000) using DNS (Direct Numerical Simulation) approach. The simulations are performed at a high angle of attack in gliding mode replicating the owl’s wing position during the approach phase towards the prey. This comparative study enables us to shed light on the impact these serrations have on the flow dynamics developed over the wing. Disparities in the flow turbulence characteristics, as well as boundary layer parameters, are evaluated to understand how the owls’ leading-edge serrations impact the incoming flow. We will demonstrate that the presence of serrations alters the small scales of the flow in the near wake. In addition, detailed analysis of their impact on the aerodynamic performance will be presented.