Non-harmonic Root-pitch Individual-blade Control for the Reduction of Blade-vortex Interaction Noise in Rotorcraft

Open Access
Author:
Malovrh, Brendon
Graduate Program:
Aerospace Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 17, 2010
Committee Members:
  • Dr Farhan Gandhi, Dissertation Advisor
  • Dr Farhan Gandhi, Committee Chair
  • Kenneth Steven Brentner, Committee Member
  • Edward A Smith, Committee Member
  • Christopher Rahn, Committee Member
  • George A Lesieutre, Committee Member
  • Kevin James Noonan, Special Member
Keywords:
  • Blade-Vortex Interaction
  • BVI
  • noise
  • acoustic
  • helicopter
Abstract:
One of the greatest obstacles to public acceptance of rotorcraft is the high levels of noise they produce, particularly in low-speed descent. In this flight condition, the trailing edge vortex of one blade often passes in close proximity to other blades resulting in impulsive changes in lift. This Blade-Vortex Interaction (BVI) creates high levels of both noise and vibration. The objective of this dissertation is to evaluate the effectiveness of using physically motivated pulse-type Individual Blade Control for reducing the noise associated with the BVI. First, the major parameters that affect the severity of the interaction, such as vortex strength and blade-vortex miss-distance, are analyzed. Second, inputs designed specifically to alter the parameters previously identified as key are explored, resulting in elimination of advancing side noise and overall peak BVI Sound Pressure Level (BVISPL) reductions of up to 4.6 dB. Lastly, different feedback mechanisms for closed-loop control of IBC are examined to allow implementation of the developed inputs.