Hydrodynamic Performance of a Pitching Float Wave Energy Converter
Abstract
:1. Introduction
2. Theoretical Considerations
2.1. Converter Dynamics Model
2.2. Frequency Domain Analysis Method
2.3. Time Domain Analysis Method
2.4. Numerical Model Verification
3. Hydrodynamic Device Characteristics
3.1. Analysis of the Hydrodynamic Performance in the Frequency Domain
3.1.1. Pitching Response RAO
3.1.2. Radiation Damping
3.1.3. Wave Motivator
3.1.4. Additional Mass Force
3.2. Analysis of the Hydrodynamic Performance in the Time Domain
3.2.1. Effect of Mooring Point Position on Float Hydrodynamic Performance
3.2.2. Effect of Wave Angle on Hydrodynamic Float Performance
3.2.3. Effect of Wave Period on Hydrodynamic Float Performance
3.3. Irregular Waves
3.3.1. Effect of Mooring Point Position on Hydrodynamic Float Performance
3.3.2. Effect of Wave Angle on Hydrodynamic Float Performance
3.3.3. Effect of Start and End Frequency on Hydrodynamic Float Performance
4. Conclusions
- (1)
- The frequency hydrodynamic performance of the designed float conforms to the specifications of a marine mobile platform, with excellent pitching response performance. It was verified that the float radiation damping coefficient, additional mass force, and wave excitation yielded optimum pitching performance.
- (2)
- Under regular wave conditions, mooring point positions that were closer to the center of mass resulted in better device stability. The angle arrangement of the anchor-chain mooring method fully conformed to the safety requirements. The 45° wave direction angle subjected the unit to the greatest overall force with the most intense movement. Wave cycles that were closest to the peak period resulted in a larger overall force on the device and more intense movement, with a maximum force of 4061.34 N for a wave period of 2.7 s. The device can therefore operate safely, steadily, and with high reliability under all tested operating conditions.
- (3)
- Under irregular wave conditions, mooring point positions that were closer to the center of mass also resulted in better device stability. The angle arrangement of the anchor-chain mooring method fully conformed to the safety requirements. A 45° wave direction angle resulted in the greatest overall force on the unit and the most intense movement. The irregular wave frequency area at 2.5–3.0 rad/s yielded the most concentrated energy, the most force ingested by the float, and the most intense movement. The device was deemed to operate safely, steadily, and with high reliability under all operating conditions.
- (4)
- The superior performance of the pitching float-type wave power generator was verified based on the frequency and time-domain analysis. These results are significant for the use of wave-energy generators in the South China Sea and expansion of the wave-energy capture range.
Author Contributions
Funding
Conflicts of Interest
Appendix A
Float Number | Location of Mooring Point | Wave Direction (deg) | Wave Period (s) |
---|---|---|---|
1 | centroid | 0° | 2.5 |
2 | centroid | 0° | 2.6 |
3 | centroid | 0° | 2.7 |
4 | centroid | 0° | 6 |
5 | centroid | 45° | 2.5 |
6 | centroid | 45° | 2.6 |
7 | centroid | 45° | 2.7 |
8 | centroid | 45° | 6 |
9 | centroid | 90° | 2.5 |
10 | centroid | 90° | 2.6 |
11 | centroid | 90° | 2.7 |
12 | centroid | 90° | 6 |
13 | waterline | 0° | 2.5 |
14 | waterline | 0° | 2.6 |
15 | waterline | 0° | 2.7 |
16 | waterline | 0° | 6 |
17 | waterline | 45° | 2.5 |
18 | waterline | 45° | 2.6 |
19 | waterline | 45° | 2.7 |
20 | waterline | 45° | 6 |
21 | waterline | 90° | 2.5 |
22 | waterline | 90° | 2.6 |
23 | waterline | 90° | 2.7 |
24 | waterline | 90° | 6 |
25 | vertex | 0° | 2.5 |
26 | vertex | 0° | 2.6 |
27 | vertex | 0° | 2.7 |
28 | vertex | 0° | 6 |
29 | vertex | 45° | 2.5 |
30 | vertex | 45° | 2.6 |
31 | vertex | 45° | 2.7 |
32 | vertex | 45° | 6 |
33 | vertex | 90° | 2.5 |
34 | vertex | 90° | 2.6 |
35 | vertex | 90° | 2.7 |
36 | vertex | 90° | 6 |
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Float Number | Regular Wave Period (s) | Irregular Wave Period (rad/s) |
---|---|---|
1 | - | 1.5–2.5 |
2 | 2.5 | 2.0–2.5 |
3 | 2.6 | 2.5–3.0 |
4 | 2.7 | 2.0–3.0 |
5 | 6.0 | 2.5–4.0 |
Contrasting Terms | Float Number | Mooring Point Location | Wave Direction (º) | Frequency Region of Irregular Wave (rad/s) |
---|---|---|---|---|
Mooring point | 1 | Centroid | 0° | 1.5–2.5 |
Mooring point | 16 | Waterline | 0° | 1.5–2.5 |
Mooring point | 31 | Vertex | 0° | 1.5–2.5 |
Wave direction | 1 | Centroid | 0° | 1.5–2.5 |
Wave direction | 16 | Centroid | 45° | 1.5–2.5 |
Wave direction | 31 | Centroid | 90° | 1.5–2.5 |
Frequency region | 1 | Centroid | 0° | 1.5–2.5 |
Frequency region | 2 | Centroid | 0° | 2.0–2.5 |
Frequency region | 3 | Centroid | 0° | 2.5–3.0 |
Frequency region | 4 | Centroid | 0° | 2.0–3.0 |
Frequency region | 5 | Centroid | 0° | 2.5–4.0 |
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Ma, Y.; Ai, S.; Yang, L.; Zhang, A.; Liu, S.; Zhou, B. Hydrodynamic Performance of a Pitching Float Wave Energy Converter. Energies 2020, 13, 1801. https://doi.org/10.3390/en13071801
Ma Y, Ai S, Yang L, Zhang A, Liu S, Zhou B. Hydrodynamic Performance of a Pitching Float Wave Energy Converter. Energies. 2020; 13(7):1801. https://doi.org/10.3390/en13071801
Chicago/Turabian StyleMa, Yong, Shan Ai, Lele Yang, Aiming Zhang, Sen Liu, and Binghao Zhou. 2020. "Hydrodynamic Performance of a Pitching Float Wave Energy Converter" Energies 13, no. 7: 1801. https://doi.org/10.3390/en13071801