The Influence of Static Active Twist Control on BVI Noise in Descent Flight

Abstract

Active twist control uses piezoceramic actuators in order to generate a control input at the blade. These actuators are operated within an asymmetric voltage range. Thus, static control inputs are needed to be able to use the full operational range of the actuators. This paper investigates the influence of static active twist control on vortex parameters which mainly determine the intensity of blade vortex interactions (BVI) and therefore the noise radiated in descent flight. A numerical study is carried out with DLR's aeromechanics rotor simulation code S4. Within the scope of this study, the effect of different static twist inputs on vortex parameters in dependence of the rotor angle of attack is analysed. Variations in BVI noise are then demonstrated for selected static active twist control inputs based on sound pressure levels that have been computed using DLR's acoustic code APSIM. The aim of this study is an understanding of the influence of static active twist control on the driving parameters for BVI noise and an evaluation of the resulting variation in BVI noise itself.