Wave Focalization in a Wave Tank by Using Time Reversal Technique

Offshore structures design and validation currently involves complex numerical simulations and experimental verifications using reduced models. These experiments are usually conducted in ocean wave tanks. The wave focalization using time reversal is a well-known technique in the field of acoustics. It was proved using several physical waves, but was not experimentally tested in ocean wave in the scale of a wave tank. For this purpose, the tank of the University of Sao Paulo was used for these experiments. The tank has 148 flaps equipped with wave probes for control feedback of active wave absorption. Hence, the waves can be recorded and re-emitted by the flaps. The time reversal technique is here experimentally evaluated in order to generate focused waves in water tests. First, a small object dropping into the tank water acts as a source of impulsive wave for time reversal experiments. In a second experiment, a reflective wall is introduced into the tank, in order to distort the wave propagation and generate wave reverberations. The results show the ability of the time reversal technique to focalize impulsive waves back at the origin, even in the case of obstacles to the wave propagation.