TY - GEN
T1 - Stability Analysis of Whirl Flutter in a Nonlinear Gimballed Rotor-Nacelle System
AU - Mair, Chris
AU - Rezgui, Djamel
AU - Titurus, Branislav
PY - 2019/6/7
Y1 - 2019/6/7
N2 - Whirl flutter is an aeroelastic instability that affects propellers/rotors and the aircraft on which they are mounted. The complexity of its behaviour and analysis increases significantly with the addition of nonlinear effects. With their long and flexible rotor blades, tiltrotor aircraft are particularly susceptible. This paper investigates the impact of structural nonlinearity on the whirl flutter stability of a basic gimballed rotor-nacelle model, compared to a baseline linear stiffness version. A 9-DoF model with quasi-steady aerodynamics and blades that can move both cyclically and collectively in both flapping and lead-lag motions was adopted from existing literature. The nonlinearities investigated in this paper are cubic and quintic softening and hardening introduced to the gimbal flapping stiffness. The investigation is conducted through a combination of bifurcation and eigenvalue analyses, supplemented by time simulations. In some cases, the nonlinearities are shown to cause whirl flutter behaviour to exist in parameter value regions that are predicted to be stable by linear analysis. This impact is fully captured in the redrawn system stability boundary.
AB - Whirl flutter is an aeroelastic instability that affects propellers/rotors and the aircraft on which they are mounted. The complexity of its behaviour and analysis increases significantly with the addition of nonlinear effects. With their long and flexible rotor blades, tiltrotor aircraft are particularly susceptible. This paper investigates the impact of structural nonlinearity on the whirl flutter stability of a basic gimballed rotor-nacelle model, compared to a baseline linear stiffness version. A 9-DoF model with quasi-steady aerodynamics and blades that can move both cyclically and collectively in both flapping and lead-lag motions was adopted from existing literature. The nonlinearities investigated in this paper are cubic and quintic softening and hardening introduced to the gimbal flapping stiffness. The investigation is conducted through a combination of bifurcation and eigenvalue analyses, supplemented by time simulations. In some cases, the nonlinearities are shown to cause whirl flutter behaviour to exist in parameter value regions that are predicted to be stable by linear analysis. This impact is fully captured in the redrawn system stability boundary.
KW - Whirl flutter
KW - gimballed rotor
KW - Stability
KW - Bifurcation analysis
KW - continuation method
UR - http://www.scopus.com/inward/record.url?scp=85069457858&partnerID=8YFLogxK
M3 - Conference Contribution (Conference Proceeding)
T3 - Annual Forum Proceedings
SP - 1
EP - 16
BT - Proceedings of the 75th Forum of the Vertical Flight Society
PB - Vertical Flight Society
CY - Philadelphia, Pennsylvania
T2 - Vertical Flight Society's 75th Annual Forum and Technology Display
Y2 - 13 May 2019 through 16 May 2019
ER -