Blade-Vortex Interaction Noise Mitigation via Smart Materials Technology

Controlling main rotor blade-vortex interaction (BVI) noise is a central issue both in detectability of military helicopters and community acceptance of rotorcraft operations. Research to date has produced substantial insight into the BVI phenomenon, though attemps to formulate practical design or active control strategies to reduce BVI noise without significant performance degradation have met with limited success. This proposal involves the development of innovative methods for applying on-blade control using Shape Memory Alloy (SMA) smart materials technology to tailor blade loading, deformation, and wake structure to minimize BVI noise in key flight conditions without incurring prohibitive penalties in performance, vibration, or cost. Recent advances in actuation of control surfaces with SMA-driven devices have made feasible a variety of on-blade control concepts for noise reduction and have brought the goal of a variable design blade - optimized to minimize noise in critical flight conditions within reach. Advanced computational aerodynamic models will be used both to assess several candidate on-blade control techniques and to provide insight into BVI events. The proposed effort will involve validation of these models followed by parametric design studies of several SMA-based control devices, laying the groundwork for eventual demonstration of successful concepts at model scale. BENEFITS: The noise control technology to be developed here would have direct application to mitigating the strong BVI noise generated during helicopter landing and approach. Such noise poses an enormous operational difficulty for the rotorcraft industry, and a viable control mechanism for BVI noise and vibration would address one of the industry's most important challenges in community acceptance and passenger comfort.