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This paper investigates the energy production of a “meso-scale”, wind-based energy harvester that exploits the torsional aeroelastic instability of a rigid blade-airfoil, elastically supported at equidistant supports. Torsional flutter is a single mode aeroelastic instability phenomenon, in which a diverging dynamic angular rotation of a body occurs. The apparatus relies on a simple mechanism that uses flow-induced pitch motion to extract and convert airflow kinetic energy to electrical energy. The system is composed by a rigid blade-airfoil, connected to a support structure through a non-linear restoring force (torsional spring-like) mechanism that enables the rotation about a reference pivot axis. The proposed technology is designed to be efficient in the range of low and medium wind speeds (10-13 m/s), in which horizontal-axis wind turbines and other harvesters are not efficient. Deterministic pre-flutter, incipient flutter and post-critical vibrations of the apparatus have been already explored in a previous study. This work aims to further investigate the aeroelastic behavior of the “flapping foil” by examining the effect of turbulence, random experimental error and modeling simplifications of the aeroelastic forces. The analysis is conducted at incipient flutter in the frequency domain using classical unsteady force models. Monte Carlo methods are employed to solve for the probability of incipient flutter speed. Several configurations are considered to improve the efficiency of the energy harvester.
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Exploring Stochastic Dynamics and Stability of an Aeroelastic Harvester Contaminated by Wind Turbulence and Uncertain Aeroelastic Loads
The paper expands a recently developed model that examines the stochastic stability of a torsional-flutter-based harvester. The new model accounts for both uncertainty in the aeroelastic loads and wind turbulence in the incoming flow. Since the blade-airfoil is three-dimensional, three-dimensional flow effect are simulated through η3D, i.e., a reduction parameter of the static lift slope, dependent on the aspect ratio of the apparatus. The first uncertainty source is a byproduct of the modelling simplifications of the aeroelastic loads, which are described by indicial function approach and ideally applicable to two-dimensional flow. The second source is the flow turbulence that operates by modifying the Parametric stochastic perturbations are applied to the parameter describing the memory-effect of the load, simulating “imperfections” in the load measurement and approximate description through η3D. Stochastic flutter stability is examined by mean squares. Post-critical states are also discussed.
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- Award ID(s):
- 2020063
- PAR ID:
- 10395772
- Date Published:
- Journal Name:
- 8th European African Conference on Wind Engineering, Bucharest, Romania, September 20-23, 2022. Conspress, 2022, ISBN 978-973-100-532-4
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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