Implementation of a Digital Filter for Active Wave Absorption Systems in a wave flume

This note reviews the theoretical framework for active wave absorption, trying to give a physical understanding of the basic concepts, and in particular of the transfer functions between the paddle motion and the free-surface elevation measured in front of the paddle. A FIR digital filter is designed to carry out the 2D active wave absorption. A filter matching the exact theoretical transfer function is non-causal and would necessarily require future knowledge of the signal. The filter noncausal part is necessarily removed by truncation and this truncation inevitably distorts both magnitude and phase, but there are ways to preserve most of its effectiveness. The resulting impulse response is compared to the analogic filter used in the lab. The purpose of the paper is to define a suitable filter to substitute the existing analogic one. The new filter is optimized and targeted to the existing constraints. The research, conducted at the Maritime Laboratory of the University of Padua is related to the new wave generator under development.