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Influence of dynamic inflow states on coupled rotor fuselage modes
Salini S. Nair,
Published in American Helicopter Society
2017
Volume: 62
   
Issue: 4
Abstract
This paper addresses how dynamic inflow, while improving the correlation with ground-resonance measurements, could make the mode identification of the rotor-body-inflow system demanding. Specifically, the paper demonstrates dynamic inflow effects on the modes of two earlier tested configurations: configuration 1 with a nonmatched stiffness rotor (nonrotating flap and lag stiffnesses are unequal) and configuration 4 with a matched stiffness rotor (these stiffnesses are equal). The experimental model represents a three-bladed hingeless rotor on gimbal support; the blades are rigid, and they have spring-restrained flap-lag hinges; and the gimbal permits roll and pitch motions. The mode identification is based on relative participation of different states in the eigenvector, modal frequency and phase information about these states. For configuration 4, for instance, one of the modes has dominant contributions from multiblade flap cosine and sine states and appreciable contributions from body roll and pitch states and also first harmonic wake states; this mode is identified as the regressive flap mode (RFM), and another mode with fairly comparable characteristics is identified as the inflow mode. The phase differences between these flap states, and between these wake states, are used to distinguish RFM from the inflow mode. The phase information that is exercised herein represents a novelty of this work. © 2017 AHS International.
About the journal
JournalJournal of the American Helicopter Society
PublisherAmerican Helicopter Society
ISSN00028711
Open AccessNo
Concepts (11)
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    Stiffness
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    Wakes
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    COUPLED ROTORS
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    Dominant contributions
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    EXPERIMENTAL MODELING
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    GROUND RESONANCE
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    Modal frequency
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    MODE IDENTIFICATION
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    Phase difference
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    PHASE INFORMATION
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    Rigid rotors