CFD DRAG AND POWER PREDICTION FOR A ROTOR IN HOVER OR FORWARD FLIGHT. FORMULATION AND FIRST APPLICATIONS

Two general formulations based on the conservation of momentum equations are developed in this paper with the ultimate goal to predict the power consumed by a rotor. The first formulation concerns forward flight configurations for which the inviscid flow-field around the blades is calculated using the 3D unsteady Full Potential equations and the second one concerns hover configurations modeled using a 3D Euler solver. In each case, the computational method can be coupled to a 3D laminar-turbulent boundary layer code in order to have access to the viscous drag. The theoretical aspects are first validated, then applied to non-lifting as well as lifting configurations. Results in forward flight present a reasonable agreement with experiment (for the torque prediction). In hover, the database used for the comparisons did not include values for the power consumed by the rotor. This study shows that drag and power predictions with the use of CFD methods for helicopter configurations is not unrealistic and can bring a better understanding of the drag production mechanisms.