Leading-edge tubercles applied onto a flapped rudder

The addition of a trailing edge flap is an effective way to enhance the lift generated by marine rudders. This is achieved through camber being introduced into the foil section when the flap is deflected. But the strong curvature in the flow around the flap’s leading edge makes it prone to early flow separation and increased drag. Leading-edge tubercles offer a means to control flow separation whilst improving lifting performance at post- stall angles of attack (AOA). Therefore, this study aims to investigate the tubercle leading edge's (TLE) ability to improve the hydrodynamic performance of a flapped rudder. A finite-span reference rudder with a 20% trailing-edge flap and its TLE modification were numerically analysed using Detached Eddy Simulations (DES) for fully turbulent flow at a Reynolds number of 1.15×10^6.

Flow separation severity and progression were controlled and minimised through the TLE modifications. As a result, the TLE rudder produced up to 15% higher maximum lift and up to 25% more post-stall lift. The rudder efficiency also improved for various rudder and flap angle combinations.