Seminars

The next generation of vertical lift vehicles will require large increases in speed in range without compromising hover efficiency. Coaxial compound helicopters can reach speeds up to 250kt, which is a 50% improvement over traditional configurations. At these speeds rotor drag, including a significant portion originating from the reverse flow region, is a factor limiting vehicle performance.

A modification to the blades consisting of a deformable trailing edge is proposed to reduce blade drag in the reverse flow region. The drag reduction potential of the deformed trailing edge is first demonstrated on 2D airfoil sections through wind tunnel tests and computational fluid dynamics simulations.

Overset grid Reynolds averaged Navier-Stokes simulations and vortex particle simulations are used to simulate the full rotor of the X2 Technology Demonstrator helicopter rotor as well as a rotor utilizing the deformed trailing edge at a 230kt flight condition.  The blade modification is shown to have significant effects on the rotor performance.  Several challenges in modeling rotors in these conditions are highlighted including capturing transonic flow, regions of laminar and turbulent flow, and regions of stalled and separated flow.