Abstract
Wave energy, with its high energy density and predictability, holds significant potential in renewable energy. Among various wave energy converters (WECs), oscillating water column (OWC) devices are particularly attractive due to their structural simplicity and operational reliability. This study experimentally investigates the performance enhancement of a floating backward-bent duct buoy (BBDB) OWC through the integration of a damping plate. The results show that the damping plate increases pneumatic power output by selectively attenuating heave and pitch motions while amplifying the oscillation of the internal water surface (IWS). It also lengthens the natural pitch period, thereby extending the effective energy capture bandwidth toward longer waves. Although mooring constraints generally reduce energy capture, they can enhance performance under long-period conditions where the BBDB motion is less dominant. Tests with different plate lengths reveal that the configuration with d1/d2 = 0.10 yields the most favorable performance, with the maximum capture width ratio (CWR) reaching 1.43 at a wave amplitude of 0.015 m and a period of 1.3 s. Across a range of wave periods and amplitudes, the captured power follows a clear power-law dependence on wave amplitude, and the damping plate appears to alleviate efficiency degradation with increasing wave height under multi-frequency conditions. Under irregular waves, the damping plate model exhibits markedly improved performance for waves incident from the designed wave-facing direction. It also maintains a distinct advantage in the long-period range for waves approaching the bent duct opening, highlighting enhanced bandwidth coverage and strong potential for real-sea energy conversion.