Computational Analysis of the W3 Sokol Rotor with Gurney Flaps

摘要

In recent years the implementation of passive and active Gurney flaps on rotors is studied to enhance hover and forward flight performance. The use of a Gurney flap on a helicopter rotor provides a mechanism for obtaining local changes to the aerodynamic properties of the blade sections. This can be used to alter the lift distribution along the blade in hover or forward flight and can also be combined with the dynamic properties of the blade to allow for beneficial aeroelastic deformation of the baseline blade shape. The Gurney flap works by providing further stagnation area near the trailing edge of he blade that benefits lift. On the other hand, the pitching moment coefficient is increased and unless the Gurney is sized carefully, substantial drag penalties may also occur. In this work, the effect of a Gurney flap is studied on the main rotor of the W3 Sokol helicopter. The Gurney flap is modelled by flagging any block face within the computational mesh occupied by the flap with a solid, no slip boundary condition. This method is implemented in the HMB solver and is proved to be simple and effective. CFD calculations were performed using two different geometries approximating the W3 blade. The first blade shape is made out of modified NACA23012 sections and it has a flat tip and a sharp trailing edge, while the second approximation has a round tip and a blunt trailing edge as well as a trim tab located at the 75% of the radius with a span of 10% and a trailing edge tab running from 85% of the radius up to the tip. The geometries are presented in Figure 1.