Continuation techniques for analysis of whole aeroengine dynamics with imperfect bifurcations and isolated solutions

Salles, Loïc; Staples, B; Hoffmann, Norbert; Schwingshackl, Christoph W.

doi:10.1007/s11071-016-3003-y

Cited by 44 publications

(20 citation statements)

References 24 publications

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“…Salles et al [32] used HBM and numerical continuation to obtain the bifurcation diagram of an entire aeroengine with three shaft and four snubber elements. Component mode synthesis was used to reduce the FE model, which was further reduced to the nonlinear degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

“…Aside from experimental investigations, the primary tools for understanding rotordynamics have thus far been time simulation [5][6][7]12,34,37,39] and analytical and semi-analytical approaches based on the harmonic balance method [29,30,32,35,38]. The time simulation approach is slow; solutions must be continued for some arbitrary amount of time to converge to a steady state which make it excessively time-consuming for low damping cases [33].…”

Section: Introductionmentioning

confidence: 99%

“…The continuation method is applied directly to the systems of ODE, in contrast to Refs. [29,32,38]. The autonomous rotating coordinate frame equations of motion are used in the numerical continuation procedures; the observed periodic solution families correspond to quasi-periodic solutions in the stationary frame.…”

Section: Introductionmentioning

confidence: 99%

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Continuation analysis of a nonlinear rotor system

2021

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Nonlinearities in rotating systems have been seen to cause a wide variety of rich phenomena; however, the understanding of these phenomena has been limited because numerical approaches typically rely on “brute force” time simulation, which is slow due to issues of step size and settling time, cannot locate unstable solution families, and may miss key responses if the correct initial conditions are not used. This work uses numerical continuation to explore the responses of such systems in a more systematic way. A simple isotropic rotor system with a smooth nonlinearity is studied, and the rotating frame is used to obtain periodic solutions. Asynchronous responses with oscillating amplitude are seen to initiate at certain drive speeds due to internal resonance, in a manner similar to that observed for nonsmooth rotor–stator contact systems in the previous literature. These responses are isolated, in the sense that they will only meet the more trivial synchronous responses in the limit of zero damping and out of balance forcing. In addition to increasing our understanding of the responses of these systems, the work establishes the potential of numerical continuation as a tool to systematically explore the responses of nonlinear rotor systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Continuation analysis of a nonlinear rotor system

2021

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“…Continuation methods were also used in the AW159/Wildcat Release to Service document [18,19], to investigate free-play effects on the behaviour of the tail rotor. Salles et al [20] used continuation and bifurcation methods to investigate bifurcations in the behaviour of whole engine rotordynamic models, due to the presence of nonlinearities, although their analysis was conducted in the frequency domain.…”

Section: Introductionmentioning

confidence: 99%

“…Salles et al. [20] used continuation and bifurcation methods to investigate bifurcations in the behaviour of whole engine rotordynamic models, due to the presence of nonlinearities, although their analysis was conducted in the frequency domain.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear stability analysis of whirl flutter in a rotor-nacelle system

2018

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Whirl flutter is an aeroelastic instability that affects propellers/rotors and the surrounding airframe structure on which they are mounted. Whirl flutter analysis gets progressively more complicated with the addition of nonlinear effects. This paper investigates the impact of nonlinear pylon stiffness on the whirl flutter stability of a basic rotor-nacelle model, compared to a baseline linear stiffness version. The use of suitable nonlinear analysis techniques to address such a nonlinear model is also demonstrated. Three types of nonlinearity were investigated in this paper: cubic softening, cubic hardening and a combined cubic softening-quintic hardening case. The investigation was conducted through a combination of eigenvalue and bifurcation analyses, supplemented by time simulations, in order to fully capture the effects of nonlinear stiffness on the dynamic behaviour of the rotor-nacelle system. The results illustrate the coexistence of stable and unstable limit cycles and equilibria for a range of parameter values in the nonlinear cases, which are not found in the linear baseline model. These branches are connected by a number of different bifurcation types: fold, pitchfork, Hopf, homoclinic and heteroclinic. The results also demonstrate the importance of nonlinear whirl flutter models and analysis methods. Of particular interest are cases where the dynamics of the nacelle are unstable despite linear analysis predicting stable behaviour. A more complete stability envelope for the combined model was generated to take account of this phenomenon.

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Nonlinear frequency response analysis using MSC Nastran

Kumar,

Carlson,

Kumar

et al. 2024

Numerical Meth Engineering

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Frequency response analysis often provides a great deal of information about the system response over the entire range of operation. This can be computationally expensive if time‐domain methods are used, especially for large structural models. Presence of non‐linearity in the system makes it difficult to employ standard frequency response analysis techniques, which are linear in nature. If the system contains mild‐nonlinearities and the response of the system can be assumed to be periodic, it is possible to obtain nonlinear frequency response of the system using harmonic balance techniques. This paper presents the application of the harmonic balance method for solving nonlinear structural dynamics problems. To improve robustness of the solution and capture unstable branches, the continuation procedure technique is included along with the harmonic balance method. The method developed has been implemented in MSC Nastran SOL 128.

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Continuation techniques for analysis of whole aeroengine dynamics with imperfect bifurcations and isolated solutions

Cited by 44 publications

References 24 publications

Continuation analysis of a nonlinear rotor system

Continuation analysis of a nonlinear rotor system

Nonlinear stability analysis of whirl flutter in a rotor-nacelle system

Nonlinear frequency response analysis using MSC Nastran

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