Numerical Study of Non-Linear Dynamic Behavior of an Asymmetric Rotor for Wave Energy Converter in Regular Waves

Abstract

This study conducted a numerical investigation on the non-linear motion problems between a Salter duck-type rotor and large waves using CFD simulations. Regular waves of five different wave heights were generated. First, the linear motion of the rotor from the CFD simulation was verified by comparing it with the existing experimental and frequency domain analysis results. Then, a series of CFD simulations were performed to investigate the non-linear motions of the rotor. In the case of a lower wave height, the CFD simulation results were in good agreement with the experimental and frequency domain analysis results. However, as the wave height increased, the resonance periods were different in each other. In addition, the magnitudes of normalized pitch motions by the wave heights decreased as the wave heights increased. To investigate the aforementioned phenomena, the pitch motion equation was examined using separate CFD simulations. The results showed that changing the restoring moments induced changes in the maximum pitch motions and magnitudes of the normalized pitch motions. In the case of a higher wave height, non-linear phenomena and the changing restoring moments induced non-linear motion.

Advanced Maximum Power Control Algorithm Based on a Hydraulic System for Floating Wave Energy Converters

“…Figure 8b shows a block diagram of the simulation. The input condition of the regular wave simulation was compared with the output performance when the period was changed while the wave height was 0.75 m. In the input condition, the pitch angle and absorption power of the floating body based on the load change for each period were calculated using CFD under the 0.75 m wave height condition, as shown in Figure 8 [38].…”

Experimental Study on Performance of a Wave Energy Converter Rotor with a Moving Platform

“…As shown in Figure 3, with an increase in wave height, the resonance periods of the rotor shift towards shorter wave periods, and the magnitudes of the motion RAOs decrease. This phenomenon occurs because the restoring moment of the rotor can vary based on the pitch angles of the rotor [19]. Consequently, conducting forced motion tests with increasing wave heights becomes necessary.…”

Enhancing Wave Energy Conversion Efficiency through Supervised Regression Machine Learning Models

“…This distinctive characteristic enhances overall performance, allowing for the successful conversion of both kinetic and potential energies generated by the waves into rotational mechanical energy. The evolutionary trajectory of the asymmetric WEC has witnessed the integration of experimental approaches [19][20][21] and numerical methods [22][23][24] to enhance its performance across a spectrum of sea states. Notably, the efficiency of this technology experiences a substantial decline when confronted with the intricate variations in incoming waves, encompassing factors such as high steep waves, 3D nonlinear effects, and the influence of waves breaking in the proximity of the WEC.…”

“…These dynamic wave conditions can lead to a notable reduction in efficiency. In response to these challenges, numerous researchers have used nonlinear models to investigate the complex behavior of the asymmetric WEC, uncovering factors that contribute to its suboptimal performance [22,25]. To surmount these limitations, innovative strategies have been explored, including the incorporation of mechanisms such as negative stiffness, which have shown promising results in augmenting the device's efficiency [26,27].…”