How deformable Gurney flaps combined to droop nose leading edge affecting the output power of flapping wind turbine?

Abstract

The influence of fixed and movable Gurney flaps on the aerodynamic characteristics of various devices, including flapping airfoils and vertical and horizontal axis turbines, has been widely studied. This paper presents a novel idea of Deformable Gurney Flap (DGF) combined with a Droop-Nose Leading-Edge (DNLE), which aims to enhance the output power of flapping airfoils in a reversed D configuration. The core mechanism involves actuating the DNLE to rapidly increase the drag profile with a deflection velocity (i.e. twice that of the main airfoil) thereby maximizing the power extracted via horizontal motion, $P_x\left(t\right)$. Crucially, the DNLE is deployed only when the main airfoil's motion aligns with the direction of the resultant drag force. The primary advantage of the DGF-DNLE architecture is its ability to provide complete control over the flap's aerodynamic influence throughout the complex flapping cycle. The DGF's capacity for controlled expansion and contraction allows for timely and precise adjustments to the pressure distribution, thereby optimizing the integrated lift and drag coefficients. A comprehensive numerical analysis, conducted using a two-dimensional transient simulation with an adapted dynamic mesh, demonstrated a 21 % increase in the overall output power compared to the baseline configuration.