Design and Construction of an Active Wave Absorber in a Wave Channel

An important step in the development of new ocean structures is to conduct tests on reduced scale models in tanks that reproduce the environmental conditions of their operation. For the wave modeling in a 2D channel, waves are generated in one of its end by the wave-maker and they should not be reflected back to the tested vessel. If these reflected waves were not absorbed they would interfere into the wave field and consequently interact with the body or structure under investigation, which can reduce considerably the experiment duration and the quality of its results. The simplest solution is the use of a passive beach to absorb the reflected waves, composed by a long ramp at the far end of the channel. As an alternative to these conventional beaches, wave-makers equipped with a designed control system can be used as active absorbers. These so-called active beaches have the advantage that they do not extend into the experimental domain of the basin and, at least in linear theory, low or zero reflection could be achieved. The objective of the present work is to design and construct an active wave absorption system into LOC, Laboratory of Waves and Currents, at COPPE/UFRJ, considering a wave field over the channel with no body or structure interaction. First results showed an absorption level comparable with the passive beach, however a careful tuning process is necessary to minimize the reflection coefficient.