The Wake Geometry of a Hovering Helicopter Rotor and Its Influence on Rotor Performance

Abstract

Systematic model rotor performance and wake geometry data were acquired to evaluate the influence of wake geometry on rotor hover performance. Analysis of the wake data resulted in (1) the development of a simple generalized representation of the near wake which facilitates the rapid estimation of realistic wake geometries for a wide range of rotor designs and operating conditions and (2) the discovery of a reduction in wake stability with increasing distance from the rotor. The results of a theoretical method for predicting the wake geometry are also presented. Results of a prescribed wake analysis for predicting rotor hovering performance show that the incorporation of a realistic wake geometry provides significantly improved predictions of rotor performance characteristics. Finally, initial results of advanced experimental techniques for determining rotor make characteristics are presented dong with a brief discussian of other current efforts at UARL pertaining to rotor make geometry and performance.