| A Navier-Stokes/full potential methodology has been developed for the efficient prediction of three dimensional unsteady viscous flow phenomena that occur over helicopter rotors in forward flight. The method is a hybrid approach that combines a Navier-Stokes solver modeling the viscous flow over the blade and the near wake, with a potential flow solver for the inviscid isentropic flow in the far field. In forward flight, CPU time is reduced by resolving a single blade rather than the entire rotor system as typically done in other wake capturing CFD codes. The influences of the other blades are modeled as a collection of bound and tip vortices. A grid motion module has been developed to account for the blade motion and elastic deformations. Free and prescribed wake models have been developed to model the tip vortex effects once the tip vortex leaves the viscous flow region and enters the potential flow region. This hybrid method has been used to compute the blade loads from first principles, while including the influences of the elastic deformation and the blade vortex interactions.; A two-bladed AH-1G rotor at a low advance ratio has been studied, and the results compared with flight test data and experimental data. Flow over a model UH-60A rotor in high speed forward flight has also been studied. Comparisons with experiments and other numerical simulations are presented. |
