USP Active Absorption Basin: Absorption of Irregular Waves

The implementation of active absorption of irregular waves in USP Active Absorption Basin is described. The algorithm control is based on the method proposed by Scha¨ffer. A digital filter is applied as time realization of a frequency domain absorption transfer function using the measurement of surface elevation at each wavemaker as the hydrodynamic feedback. Motor dynamics and delay due to signals time travel were compensated to increase the absorption efficiency. Experiments with regular and irregular waves were carried out, where the results show a good agreement between predicted theoretical reflection coefficient and experimental values. Reflection coefficient smaller than 10% were obtained for waves in the frequency range of 0.4 to 1.1 Hz.