Active wave absorption method for force-controlled wavemakers based on amplitude–phase fitting

Reflected waves at flume boundaries adversely affect the accuracy of wave simulation experiments, motivating the development of active absorption techniques. The absorption methods of force-controlled wavemakers, however, remain limited due to the complexity of their transfer functions. This study first derives the absorption transfer functions of piston-type and flap-type wavemakers in the frequency domain based on force control, and then uses them to design an active absorption system based on infinite impulse response (IIR) filters. A filter with the appropriate design is derived by fitting the magnitude and phase responses to the transfer function by using the least-squares method for the frequency domain. Numerical results show that the proposed IIR filter can absorb waves over a wide range of frequencies, especially in the 0.3–1.4 Hz band, with an efficiency exceeding 95%. Compared with a method proposed in previous studies, the proposed filter delivers significantly improved absorption performance in the high-frequency range. Validation under regular and irregular wave conditions demonstrates that the proposed active absorption system for force-controlled wavemakers not only achieves high absorption efficiency in good agreement with theoretical predictions, but also exhibits satisfactory robustness to noise interference and maintains stable performance during long-duration operation.