Beating vibration phenomenon of a very large floating structure

Abstract

When a very large floating structure (VLFS) is subjected to successive regular waves, it may sometimes suffer from “beating vibration”. This phenomenon occurs when the wave period approaches the natural periods of the structure. The beating action occurs with the period far longer than the incident wave period and sometimes has a conspicuous ups and downs. The vibration amplitude due to regular wave will be alternatively increased and decreased as the synergistic effect caused by the beating. The mechanism of the beating vibration has been investigated through FEM simulation based on the time-domain analysis then the example cases of beating phenomena are demonstrated focusing on the VLFS which was preliminarily designed as a supply base for a deep ocean. It has turned out that the fundamental characteristics of the beating action are mainly contributed by the magnitude of period gap between the incident wave and the natural period of the structure, and also by the magnitude of the damping force.