**4. Experimental Method**

The experiment was carried out in a subsonic closed recirculation wind tunnel. The design range of the flow velocity at the working section of the tunnel was 1–22 m/s, with the turbulence intensity not exceeding 0.5%. The layout of the experiment is shown in Figure 5. When exploring the influence of the external resistance *RL*, the external load resistance of 10 kΩ–1 MΩ was connected in sequence, and the wind tunnel control speed changed in a gradient of 3 m/s–10 m/s. The output voltage was collected and stored by a data acquisition instrument (NI 9234). The highest sampling frequency was 2840 Hz for acquisition, and the acquisition time exceeded 120 s. The voltage and displacement were inputted into labview for visual observation and analysis. The displacement of the transmission-line-like flexible structure was monitored by a laser displacement sensor that was installed on the side wall of the wind tunnel. The output voltage of the harvester was recorded when the vibration of the flexible structure became stable.

**Figure 5.** Experimental setup: (**a**) working section; (**b**) control platform.
