NAVIER-STOKES SIMULATIONS OF TIP VORTICES FOR FIXED AND ROTATING HELICOPTER BLADES'

Flowfield and tip vortex results are presented for hovering rotor blade at sub-critical and supercritical flow conditions for both nonlifting and lifting configu-rations. These results are calculated numerically by solving, in a time-accurate fashion, the unsteady thin layer Navier-stokes equations written in rotor coordi-nates. The lifting calculations use an induced downwash correction,estimated from a free wake analysis, to the geometric angle of attack of the blades to account for the wake effect. Comparison of numerical results with the exper-imental data shows very good agreement for all cases considered. Alternate methods of calculating hovering rotor flowfield as steady state flowfield on iso-lated fixed-blade that have the same ciculation distribution as that of rotor in hover are explored. Comparison of these results with the rotor results indi-cate that centrifugal forces of the rotating blade have negligible influence on the overall flowfield at both subcritical and supercritical flow conditions. The results presented in this study are computed on a CRAY2 supercomputer. 1