## 3 Results and Discussions
### Adaptability under Multiple Kinetic Parameters
At a relative heaving amplitude of 0.6, both tail configurations, with and without a cylinder, exhibit the best energy harvesting efficiency. Specifically, the optimal efficiency of the foil with the cylindrical spoiler structure is 5.68% higher than the one without under the same working conditions. Additionally, the maximum enhancement in energy harvesting efficiency occurs when the relative heaving amplitude is 1.4, reaching up to 21.60%. Consequently, the new flow control method, involving the use of a trailing edge cylindrical spoiler structure, is demonstrated to be effective for enhancing the oscillating foil performance across different relative heaving amplitudes. In Figure 17, the effects of pitching amplitudes (\(\theta_{0}\)) on the energy harvesting performance for the oscillating foil with and without a cylindrical spoiler structure at the trailing  
Figure 16: Energy harvesting efficiency of the oscillating foil with/without a cylindrical spoiler structure at the trailing edge for different relative heaving amplitudes. Figure 15: Energy harvesting efficiency of the oscillating foil with/without a cylindrical spoiler structure at the trailing edge for different reduced frequencies. edge are illustrated. The pitching amplitude ranges from 50\({}^{\circ}\) to 90\({}^{\circ}\), while maintaining the structural parameters of the turbulence cylinder at the trailing edge unchanged, and all the other parameters consistent with the previously outlined calculations. Under the specified pitching amplitude conditions, the efficiency of the oscillating foil with a trailing edge cylindrical spoiler structure surpasses that of the one without. The energy harvesting efficiency demonstrates an initial increase, followed by a subsequent decrease with an augmentation in the pitching amplitude. Both types of oscillating foils reach their maximum efficiency at a pitching amplitude of 75\({}^{\circ}\), with the oscillating foil equipped with the cylindrical spoiler structure exhibiting an optimal efficiency 6.20% higher than that without the same conditions. The most substantial improvement occurs at a pitching amplitude of 50\({}^{\circ}\), with an increase of 12.39%. In summary, within the operating range of pitching amplitudes from 50\({}^{\circ}\) to 90\({}^{\circ}\), the trends in energy harvesting efficiency for cylindrical and non-cylindrical oscillating foils remain consistent. Consequently, the new flow control method of enhancing energy harvesting performance through a cylindrical spoiler structure at the trailing edge is affirmed to be effective across various pitching amplitudes. The aforementioned study conducts a comparative analysis of the aerodynamic performance of the oscillating foil with and without a designated cylindrical spoiler structure at the trailing edge across different motion parameters. The outcomes affirm the efficacy of the newly proposed flow control method, employing the cylindrical spoiler structure, in augmenting the performance of the oscillating foil for varying reduced frequencies, relative heaving amplitudes, and pitching amplitudes. The integration of the cylindrical spoiler structure at the trailing edge successfully enhances the energy harvesting capability of the system, underscoring the versatility and applicability of this novel flow control method for improving the energy harvesting efficiency of oscillating foils.