A comprehensive study on unsteady effects of oscillating Gurney flaps, or microflaps, has been conducted. Twodimensional unsteady airloads for lift, moment, and drag due to an oscillating microflap were computed using a compressible Reynolds-averaged Navier-Stokes flow solver. The computational fluid dynamics results were generated with an overset-mesh approach that captures oscillatory microflap motion. Three microflap configurations were examined to determine the type most suitable in terms of actuation efficiency and practical implementation. Furthermore, a reduced-order model for the unsteady microflaps was developed based on computational fluid dynamics simulations, using the rational function approximation approach. The resulting rational function approximation model is a state-space time-domain aerodynamic model that accounts for unsteadiness, compressibility, and time-varying freestream effect. The agreement between the reduced-order model and direct computational fluid dynamics calculations was found to be excellent for a wide range of flow conditions examined. The approximate model is suitable for incorporation in a comprehensive code, from which the potential of microflaps for active control of vibrations in rotors can be determined. Open-loop control studies indicated that the microflap produces substantial vibration reduction (80 % reduction in vertical shear), whereas closed-loop control using combined harmonic inputs consisting of a sum of four harmonics (2-5/rev) reduced the vibration objective by 92 %, on a hingeless rotor configuration resembling the Messerschmitt-Bölkow-Blohm BO-105. These results confirmed the control authority and effectiveness of the microflap for vibration reduction in rotorcraft.
Computational study of microflaps with application to vibration reduction in helicopter rotors
Numerische Studie über Mikroklappen mit Anwendung auf die Schwingungsdämpfung bei Hubschrauberrotoren
AIAA Journal ; 49 , 7 ; 1450-1465
2011
16 Seiten, 25 Bilder, 2 Tabellen, 51 Quellen
Article (Journal)
English
Computational Study of Microflaps with Application to Vibration Reduction in Helicopter Rotors
Online Contents | 2011
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