Zhimiao Yan

Modeling and nonlinear analysis of piezoelectric energy harvesting from transverse galloping

A model for harvesting energy from galloping oscillations of a bar with an equilateral triangle cross-section attached to two cantilever beams is presented. The energy is harvested by attaching piezoelectric sheets to cantilever beams holding the bar. The derived nonlinear distributed-parameter model is validated with previous experimental results. The quasi-steady approximation is used to model the aerodynamic loads. The power levels that can be generated from these vibrations, and the variations of these levels with the load resistance and wind speed, are determined. Linear analysis is performed to validate the onset of galloping speed with experimental measurements. The effects of the electrical load resistance on the onset of galloping are then investigated. The results show that the electrical load resistance affects the onset speed of galloping. A nonlinear analysis is also performed to determine the effects of the electrical load resistance and the nonlinear torsional spring on the level of the harvested power. The results show that maximum levels of harvested power are accompanied by minimum transverse displacement amplitudes. It is also demonstrated that there is an optimum load resistance that maximizes the level of the harvested power.

Performance analysis of galloping-based piezoaeroelastic energy harvesters with different cross-section geometries

The concept of harvesting energy from galloping oscillations of a bluff body with different cross-section geometries attached to a cantilever beam is investigated. To convert these oscillations into electrical power, a piezoelectric transducer is attached to the transverse degree of freedom of the prismatic structure. Modal analysis is performed to determine the exact mode shapes of the structure. A coupled nonlinear distributed-parameter model is developed to determine the effects of the cross-section geometry, load resistance, and wind speed on the level of the harvester power. The quasi-steady approximation is used to model the aerodynamic loads. Linear analysis is performed to investigate the effects of the electrical load resistance and the cross-section geometry on the onset speed of galloping. The results show that the electrical load resistance and the cross-section geometry affect significantly the onset speed of galloping. Nonlinear analysis is performed to determine the effects of the electrical load resistance, cross-section geometry, and wind speed on the system’s outputs and particularly the level of the harvested power. A comparison of the performance of the different cross sections in terms of displacement and harvested power is presented. The results show that different sections are better for harvesting energy over different regions of the flow speed. The results also show that maximum levels of harvested power are accompanied with minimum transverse displacement amplitudes for all considered (square, D, and triangular) cross-section geometries.

Piezoelectric energy harvesting from hybrid vibrations

The concept of harvesting energy from ambient and galloping vibrations of a bluff body with a triangular cross-section geometry is investigated. A piezoelectric transducer is attached to the transverse degree of freedom of the body in order to convert these vibrations to electrical energy. A coupled nonlinear distributed-parameter model is developed that takes into consideration the galloping force and moment nonlinearities and the base excitation effects. The aerodynamic loads are modeled using the quasi-steady approximation. Linear analysis is performed to determine the effects of the electrical load resistance and wind speed on the global damping and frequency of the harvester as well as on the onset of instability. Then, nonlinear analysis is performed to investigate the impact of the base acceleration, wind speed, and electrical load resistance on the performance of the harvester and the associated nonlinear phenomena that take place. The results show that, depending on the interaction between the base and galloping excitations, and the considered values of the wind speed, base acceleration, and electrical load resistance, different nonlinear phenomena arise while others disappear. Short- and open-circuit configurations for different wind speeds and base accelerations are assessed. The results show that the maximum levels of harvested power are accompanied by a minimum transverse displacement when varying the electrical load resistance.

Temperature impact on the performance of galloping-based piezoaeroelastic energy harvesters

The effects of ambient temperature on the level of harvesting energy from galloping oscillations of a bluff body are investigated. A nonlinear-distributed-parameter model is developed to determine variations in the onset speed of galloping and the level of the harvested power when the ambient temperature is varied. The considered harvester consists of a bimorph piezoelectric cantilever beam with a prismatic-structure tip mass. A modal analysis is performed to derive the exact mode shapes and natural frequencies of the beam‐structure system and their dependence on temperature variations. The quasi-steady representation is used to model the aerodynamic loads. The linear analysis shows that the temperature and the electrical load resistance affect the onset speed of galloping significantly. The nonlinear analysis shows that temperature variation affects the level of the harvested power. (Some figures may appear in colour only in the online journal)

Energy harvesting from an autoparametric vibration absorber

The combined control and energy harvesting characteristics of an autoparametric vibration absorber consisting of a base structure subjected to the external force and a cantilever beam with a tip mass are investigated. The piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear representative model is developed by using the extended Hamitons principle. The effects of the electrical load resistance on the frequency and damping ratio of the cantilever beam are analyzed. The impacts of the external force and load resistance on the structural displacements of the base structure and the beam and on the level of harvested energy are determined. The results show that the initial conditions have a significant impact on the systems response. The relatively high level of energy harvesting is not necessarily accompanied with the minimum displacements of the base structure.

Nonlinear performances of an autoparametric vibration-based piezoelastic energy harvester:

Nonlinear characterizations of an autoparametric vibration-based energy harvester are investigated. The harvester consists of a base structure subjected to an external excitation and a cantilever beam with a tip mass. Two piezoelectric sheets bounded to both sides of the cantilever beam are used to harvest the energy. The governing equations accounting for the coupled effects of the base vibration, the response of the cantilever beam and the generated power are derived. Approximate analysis of the simplified governing equations is then performed by the method of multiple scales. The usefulness of this approach is demonstrated by deriving analytical expressions for the global frequency and damping ratio of the cantilever beam. Their dependence on the electrical load resistance is quantified. Analytical expressions for the amplitudes of the base displacement and the displacement of the tip mass are derived. An expression that relates the output power to the load resistance, global damping, and displacement of the tip mass is derived. The effects of the external force and electric load resistance on the nonlinear responses of the system are determined. The results show different responses for different operational electric loads. The broadening of the excitation regime over which energy can be harvested is analyzed. The effects of the load resistance on the types of bifurcations near resonance are determined.

Nonlinear Passive Control Strategies for Suppression of Transonic Flutter

Nonlinear energy sink (NES) is used for passive control of transonic flutter of airfoil. OpenFoam is used to simulate transonic flow around the airfoil. The basic governing equation and computational methods are briefly discussed. The flow solver is validated by two classical experimental data: static RAE 2822 and oscillating NACA 64A010. The results show that rhoCentralFoam module is very effective and accurate to simulate transonic flow around the airfoil. Then, we proposed a model for aeroealstic model of the airfoil attached by NES. The analysis show that nonlinear energy sink can be used to suppress the transonic flutter of the airfoil.

Geometrically-Exact Extension of Theodorsen’s Frequency Response Model

The classical unsteady theory of Theodorsen is revisited relaxing some of the major assumptions such as (1) flat wake, (2) small angle of attack, (3) small disturbances to the mean flow components, and (4) time-invariant free-stream. A semi-analytical, geometricallyexact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. The numerical implementation of the developed model is presented. The unsteady predictions of the developed model are validated against experimental and computational results. Then, the frequency response of the flow dynamics is determined at different angles of attack. While good agreement is shown with Theodorsen’s function at small angle of attack, considerable qualitative and quantitative discrepancies between the obtained frequency response at large angles of attack and Theodorsen’s function are observed.

Nonlinear Dynamics Characterization of Piezoelectric Energy Harvesters from Hybrid Vibrations

The concept of energy harvesting from ambient and galloping vibrations of a bluff body with a triangular cross-section geometry is investigated. A coupled nonlinear distributedparameter model is developed to account for the galloping force and moment nonlinearities and the base excitation. The aerodynamic loads are modeled by using the quasi-steady approximation. Interesting nonlinear phenomena including quenching and beating phenomena are observed. To characterize the system’s nonlinearities, power spectra, phase portraits, and Poincare maps are used.