Frequency dependent decay of water waves due to floating balls with application to simulating wave decay in the marginal ice zone

Abstract

An experimental study is conducted to investigate the frequency dependent decay of free-surface water waves in a sloshing tank with partially-submerged floating plastic balls on the free-surface. The present study is motivated by the need to understand the possible mechanisms for ocean wave decay in the marginal ice zone. Laboratory experiments are performed to estimate the wave decay rate due to floating balls representing ice floes. The decay rates with the balls are sufficiently greater than the decay rates without the balls and we assume the effect of the balls dominates the decay. The temporal decay rates of the free-surface wave amplitudes are measured for a small excitation amplitude and different water-depths. The decay rates for the first and third modes of sloshing are extracted, even when these two modes are combined. It is shown that the decay rates obtained from the present study match with the exponent three power-law dependence on wave frequency as observed for the decay rates in the marginal ice zone. This matching of exponent suggests that the same mechanism may be responsible for both types of decay.