Prospects For Eulerian CFD Analysis Of Helicopter Vortex Flows

The feasibility of applying standard (Eulerian) Qnitevolume CFD algorithms to forward-Sight helicopter vortex Bows is investigated. Numerical diffusion is identified as the primary factor limiting the accuracy of such standard algorithms, making their brute-force application impractical. Recent efforts by various workers to apply compressible, finite-volume techniques to vortex-dominated problems typical of helicopter rotor Bows are aimed primarily at limiting the numerical difFusion which invariably occur with these schemes. These research efForts can be grouped into three broad categories. 1) perturbation approaches, 2) higher-order accuracy Eulerian schemes, and 3) adaptive algorithms. Existing methods for the forward-Sight problem use incompressible semi-empirical Eulerian/Lagrangian particle-tracking techniques which do not suffer from numerical diffusion. The most common problem of the Eulerian/ Lagrangian approach: restriction to incompressible, two-dimensional, and/or steady Bows, and also the need for supplementary empirical vortex-structure information are perceived as major deterrents to their continued development.