Numerical assessment of an L-shaped Gurney flap for load control

Abstract

The aerodynamic performance of a novel trailing edge L-shaped flap design is characterized numerically by means of computational fluid dynamics. The device is primarily thought for aerodynamic load adaptation to flight conditions. The device could be applied on a broad range of flying vehicles, like rotorcraft, for which it has been primarily designed, and also fixed wing aircraft and wind turbines. The operation of this movable surface is twofold. On one side, when the device is deployed downward, it acts as a Gurney flap, allowing the increase of the aerodynamic lift, without severe drawbacks in terms of drag rise. On the other side, when it is deflected upward, it is found capable to significantly alleviate the negative effects of stall. Simulations are carried out on a NACA 0012 airfoil equipped with the present L-shaped device at several angles of attack, both in linear and stall regimes. The reliability of numerical computations is supported by comparisons with pressure measurements and PIV surveys. Moreover, for small angles of attack, a Mach sensitivity analysis is performed, to assess the effects of compressibility on the L-shaped flap. Additionally, this work highlights how such device, when designed appropriately, can even delay the static stall onset.