Experimental Investigation of the Effect of Bio-Inspired Wavy Leading-Edges on Aerodynamic Performance and Flow Topologies of the Airfoil

Abstract

The characteristic of delayed airfoil stalls caused by the bio-inspired Wavy Leading-Edges (WLEs) has attracted extensive attention. This paper investigated the effect of WLEs on the aerodynamic performance and flow topologies of the airfoil through wind tunnel experiments, while also discussing the flow control mechanism of WLEs. The result shows that, at small Angle of Attack (AOA), the flow through the WLEs exhibits periodic and symmetrical characteristics, where flow vortices upwash at the trough and downwash at the crest, resulting in flow from the crest to the trough. Upwash leads to the formation of a localized three-dimensional laminar separation bubble (LSB) structure at the leading edge of the trough section. At large AOA after baseline airfoil stall, the flow on the airfoil surface of WLEs presents a two-period pattern along the spanwise direction, and the separation zone and the attachment zone appear alternately, indicating that the control effect of delayed stall is accomplished by reducing the separation zone on the airfoil surface. The alternating occurrence of the separation and attachment zones is the result of intricate interactions among flows passing through multiple WLEs. This interaction causes the convergence of high-momentum attached airflows on both sides, thereby constraining the spread of the separation from the leading edge and enabling the re-attachment of separated air. The research results of this paper provide a reference for researchers to reveal the flow control mechanism of WLEs more comprehensively.

Keywords

• wavy leading-edges
• flow topology
• luminescence oil film
• flow control