Recent Improvements to a Hybrid Method for Rotors in Forward Flight

Abstract

Ahybrid Navier ‐Stokes/full potential solver has been developed for the efe cient prediction of three-dimensional unsteady viscous e ow phenomena that occur over helicopter rotors in forward e ight. The method combines a Navier‐Stokes analysis near the blade, modeling the viscous e ow and near wake with a potential e ow analysis in the far e eld, modeling inviscid isentropic e ow. 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 account for the tip vortex effects once the vortex leaves the viscous e ow region and enters the potential e ow region. Sample results are presented for a two-bladed AH-1G rotor in descent and for a UH-60A rotor in high-speed forward e ight. Comparisons with experiments, e ight test data, and other numerical simulations are given.