Aerodynamic Performance Analysis of a Gurney Flap for Rotorcraft Application

TLDR

The study investigates the aerodynamic performance of a Gurney flap on a helicopter rotor airfoil using two‑dimensional Navier‑Stokes simulations. Static and dynamic stall characteristics were examined by comparing the Gurney‑flapped airfoil to a clean one across a range of Mach numbers, angles of attack, and flap heights, and by conducting parametric oscillation studies with the Bousman dynamic stall model. Results indicate that an optimal flap height exists that reduces drag and pitching moment while enhancing lift and lift‑to‑drag ratio, with a 2 % flap providing a balanced compromise for rotorcraft design.

Abstract

In the present study, the aerodynamic characteristics of the Gurney flap were comprehensively investigated in terms of the performance requirements for a helicopter rotor by using two-dimensional Navier-Stokes equations. To this end, with the rotor operating flow conditions in mind, the static aerodynamic characteristics of the Gurney flap are thoroughly compared with those of the clean airfoil at various Mach numbers, incidences, and Gurney flap heights. Next, to understand the general dynamic stall features of the airfoils with the Gurney flap, a series of parametric studies are performed with respect to oscillating frequency and amplitude, and the correlations of the aerodynamic coefficients are obtained by using the dynamic stall function of Bousman. It is concluded that there exists some optimum Gurney flap heights, which minimize the drag and pitching moment while maximizing the lift coefficient and lift-to-drag ratio at the same time. In the present study, the 2% Gurney flap would be a good compromise to satisfy all the major rotorcraft design criteria.