scholarly journals Flutter Control of a Two-Degrees-of-Freedom Airfoil Using a Nonlinear Tuned Vibration Absorber

2017 ◽  
Vol 12 (5) ◽  
Author(s):  
Arnaud Malher ◽  
Cyril Touzé ◽  
Olivier Doaré ◽  
Giuseppe Habib ◽  
Gaëtan Kerschen
Keyword(s):  
Limit Cycle ◽  
Large Amplitude ◽  
Degrees Of Freedom ◽  
Vibration Absorber ◽  
Aerodynamic Loads ◽  
Linear Approach ◽  
Aeroelastic Model ◽  
Large Amplitude Motions ◽  
Restoring Forces ◽  
Tuned Vibration Absorber

The influence of a nonlinear tuned vibration absorber (NLTVA) on the airfoil flutter is investigated. In particular, its effect on the instability threshold and the potential subcriticality of the bifurcation is analyzed. For that purpose, the airfoil is modeled using the classical pitch and plunge aeroelastic model together with a linear approach for the aerodynamic loads. Large amplitude motions of the airfoil are taken into account with nonlinear restoring forces for the pitch and plunge degrees-of-freedom. The two cases of a hardening and a softening spring behavior are investigated. The influence of each NLTVA parameter is studied, and an optimum tuning of these parameters is found. The study reveals the ability of the NLTVA to shift the instability, avoid its possible subcriticality, and reduce the limit cycle oscillations (LCOs) amplitude.

Generalized Modes in Time-Domain Seakeeping Calculations

2012 ◽  
Vol 56 (04) ◽  
pp. 215-233
Author(s):  
Johan T. Tuitman ◽  
Šime Malenica ◽  
Riaan van't Veer
Keyword(s):  
Rigid Body ◽  
Transient Response ◽  
Time Domain ◽  
Large Amplitude ◽  
Degrees Of Freedom ◽  
Mode Shapes ◽  
Nonlinear Load ◽  
Large Amplitude Motions ◽  
Rigid Body Modes ◽  
The Time Domain

The concept of "generalized modes" is to describe all degrees of freedom by mode shapes and not using any predefined shape, like rigid body modes. Generalized modes in seakeeping computations allow one to calculate the response of a single ship, springing, whipping, multibody interaction, etc., using a uniform approach. The generalized modes have already been used for frequency-domain seakeeping calculations by various authors. This article extents the generalized modes methodology to be used for time-domain seakeeping computations, which accounts for large-amplitude motions of the rigid-body modes. The time domain can be desirable for seakeeping computations because it is easy to include nonlinear load components and to compute transient response, like slamming and whipping. Results of multibody interaction, two barges connected by a hinge, whipping response of a ferry resulting from slamming loads, and the response of a flexible barge are presented to illustrate the theory.

Aeroelastic inverse: Estimation of aerodynamic loads during large amplitude limit cycle oscillations

2020 ◽  
Vol 98 ◽  
pp. 103131
Author(s):  
Benjamin Kirschmeier ◽  
Graham Pash ◽  
Zachary Gianikos ◽  
Albert Medina ◽  
Ashok Gopalarathnam ◽  
...  
Keyword(s):  
Limit Cycle ◽  
Large Amplitude ◽  
Limit Cycle Oscillations ◽  
Aerodynamic Loads ◽  
Inverse Estimation

scholarly journals Suppression of limit cycle oscillations using the nonlinear tuned vibration absorber

2015 ◽  
Vol 471 (2176) ◽  
pp. 20140976 ◽  
Author(s):  
G. Habib ◽  
G. Kerschen
Keyword(s):  
Limit Cycle ◽  
A Priori ◽  
Numerical Continuation ◽  
Vibration Absorber ◽  
Primary System ◽  
Mathematical Form ◽  
Limit Cycle Oscillations ◽  
Van Der Pol ◽  
Restoring Force ◽  
Tuned Vibration Absorber

The objective of this study is to mitigate, or even completely eliminate, the limit cycle oscillations in mechanical systems using a passive nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA). An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is not imposed a priori, as it is the case for most existing nonlinear absorbers. The NLTVA parameters are determined analytically using stability and bifurcation analyses, and the resulting design is validated using numerical continuation. The proposed developments are illustrated using a Van der Pol–Duffing primary system.

scholarly journals Analysis of a piecewise linear aeroelastic system with and without tuned vibration absorber

2020 ◽  
Author(s):  
János Lelkes ◽  
Tamás Kalmár-Nagy
Keyword(s):  
Wind Speed ◽  
Degrees Of Freedom ◽  
Aerodynamic Force ◽  
Piecewise Linear ◽  
Piecewise Linear Approximation ◽  
Vibration Absorber ◽  
Aeroelastic System ◽  
Stall Flutter ◽  
The Stability ◽  
Tuned Vibration Absorber

Abstract The dynamics of a two-degrees-of-freedom (pitch–plunge) aeroelastic system is investigated. The aerodynamic force is modeled as a piecewise linear function of the effective angle of attack. Conditions for admissible (existing) and virtual equilibria are determined. The stability and bifurcations of equilibria are analyzed. We find saddle-node, border collision and rapid bifurcations. The analysis shows that the pitch–plunge model with a simple piecewise linear approximation of the aerodynamic force can reproduce the transition from divergence to the complex aeroelastic phenomenon of stall flutter. A linear tuned vibration absorber is applied to increase stall flutter wind speed and eliminate limit cycle oscillations. The effect of the absorber parameters on the stability of equilibria is investigated using the Liénard–Chipart criterion. We find that with the vibration absorber the onset of the rapid bifurcation can be shifted to higher wind speed or the oscillations can be eliminated altogether.

Chaotic Motions of a Torsional Vibration Absorber

1988 ◽  
Vol 55 (4) ◽  
pp. 952-958 ◽  
Author(s):  
S. W. Shaw ◽  
S. Wiggins
Keyword(s):  
Torsional Vibration ◽  
Large Amplitude ◽  
Chaotic Dynamics ◽  
Rotating Machinery ◽  
Vibration Absorber ◽  
Chaotic Motions ◽  
Torsional Oscillations ◽  
Large Amplitude Motions ◽  
Parameter Values ◽  
Two Degree Of Freedom

We consider large amplitude motions of a pendulum-type centrifugal vibration absorber which is used for the reduction of torsional oscillations in rotating machinery. The basic two degree-of-freedom model is shown to possess chaotic dynamics for certain ranges of parameter values. The method used is a variation of Melnikov’s method (cf., Guckenheimer and Holmes, (1983), Chapter 4) developed for slowly varying oscillators (Wiggins and Holmes (1987), Wiggins and Shaw (1988)).

scholarly journals Understanding (coupled) large amplitude motions: the interplay of microwave spectroscopy, spectral modeling, and quantum chemistry

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ha Vinh Lam Nguyen ◽  
Isabelle Kleiner
Keyword(s):  
Fourier Transform ◽  
Quantum Chemistry ◽  
Large Amplitude ◽  
Environmental Chemistry ◽  
Broad Band ◽  
Microwave Spectroscopy ◽  
Rotational Spectrum ◽  
Spectral Modeling ◽  
Rotational Spectra ◽  
Large Amplitude Motions

AbstractA large variety of molecules contain large amplitude motions (LAMs), inter alia internal rotation and inversion tunneling, resulting in tunneling splittings in their rotational spectrum. We will present the modern strategy to study LAMs using a combination of molecular jet Fourier transform microwave spectroscopy, spectral modeling, and quantum chemical calculations to characterize such systems by the analysis of their rotational spectra. This interplay is particularly successful in decoding complex spectra revealing LAMs and providing reference data for fundamental physics, astrochemistry, atmospheric/environmental chemistry and analytics, or fundamental researches in physical chemistry. Addressing experimental key aspects, a brief presentation on the two most popular types of state-of-the-art Fourier transform microwave spectrometer technology, i.e., pulsed supersonic jet expansion–based spectrometers employing narrow-band pulse or broad-band chirp excitation, will be given first. Secondly, the use of quantum chemistry as a supporting tool for rotational spectroscopy will be discussed with emphasis on conformational analysis. Several computer codes for fitting rotational spectra exhibiting fine structure arising from LAMs are discussed with their advantages and drawbacks. Furthermore, a number of examples will provide an overview on the wealth of information that can be drawn from the rotational spectra, leading to new insights into the molecular structure and dynamics. The focus will be on the interpretation of potential barriers and how LAMs can act as sensors within molecules to help us understand the molecular behavior in the laboratory and nature.

scholarly journals Development of an MRE adaptive tuned vibration absorber with self-sensing capability

2015 ◽  
Vol 24 (9) ◽  
pp. 095012 ◽  
Author(s):  
Shuaishuai Sun ◽  
Jian Yang ◽  
Weihua Li ◽  
Huaxia Deng ◽  
Haiping Du ◽  
...  
Keyword(s):  
Vibration Absorber ◽  
Tuned Vibration Absorber

Vibration control using a beam-like adaptive tuned vibration absorber with an actuator-incorporated mass element

2009 ◽  
Vol 223 (7) ◽  
pp. 1555-1567 ◽  
Author(s):  
P Bonello ◽  
K H Groves
Keyword(s):  
Vibration Control ◽  
Effective Mass ◽  
Tuning Range ◽  
Excitation Frequency ◽  
Vibration Absorber ◽  
Time Varying ◽  
Additional Advantage ◽  
Expected Performance ◽  
Vibration Attenuation ◽  
Tuned Vibration Absorber

An adaptive tuned vibration absorber (ATVA) can retune itself in response to a time-varying excitation frequency, enabling effective vibration attenuation over a range of frequencies. For a wide tuning range the ATVA is best realized through the use of a beam-like structure whose mechanical properties can be adapted through servo-actuation. This is readily achieved either by repositioning the beam supports (‘moveable-supports ATVA’) or by repositioning attached masses (‘moveable-masses ATVA’), with the former design being more commonly used, despite its relative constructional complexity. No research to date has addressed the fact that the effective mass of such devices varies as they are retuned, thereby causing a variation in their attenuation capacity. This article derives both the tuned frequency and effective mass characteristics of such ATVAs through a unified non-dimensional modal-based analysis that enables the designer to quantify the expected performance for any given application. The analysis reveals that the moveable-masses concept offers significantly superior vibration attenuation. Motivated by this analysis, a novel ATVA with actuator-incorporated moveable masses is proposed, which has the additional advantage of constructional simplicity. Experimental results from a demonstrator correlate reasonably well with the theory, and vibration control tests with logic-based feedback control demonstrate the efficacy of the device.

Theoretical and Experimental Study of the Nonlinearly Coupled Heave, Pitch, and Roll Motions of a Ship in Longitudinal Waves

1993 ◽  
Author(s):  
I. G. Oh ◽  
A. H. Nayfeh ◽  
D. T. Mook
Keyword(s):  
Large Amplitude ◽  
Degrees Of Freedom ◽  
Excitation Frequency ◽  
Force Response ◽  
Governing Equations ◽  
Response Curves ◽  
Varying Coefficients ◽  
Jump Phenomena ◽  
Time Varying Coefficients ◽  
Three Degrees Of Freedom

Abstract The loss of dynamic stability and the resulting large-amplitude roll of a vessel in a head or following sea were studied theoretically and experimentally. A ship model with three degrees of freedom (roll, pitch, heave) was considered. The governing equations for the heave and pitch modes were linearized and their harmonic solutions were coupled with the nonlinear equation governing roll. The resulting equation, which has time-varying coefficients, was used to predict the response in roll. The principal parametric resonance was considered in which the excitation frequency is twice the natural frequency in roll. Force-response curves were obtained. The existence of jump phenomena and multiple stable solutions for the case of subcritical instability was observed in the experiments and found to be in good qualitative agreement with the results predicted by the theory. The experiments also revealed that the large-amplitude roll is dependent on the location of the model in the standing waves.

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