Investigations on the second-order transient gap resonance induced by focused wave groups. (1st November 2022)

• Record Type: Journal Article
• Authors: Liu, Jinshi; Gao, Junliang; Shi, Huabin; Zang, Jun; Liu, Qian
• Is Part Of: Ocean engineering. Volume 263(2022)
• Publication Date: 2022-11-01
• Subjects: Transient gap resonance -- Second-order resonance -- Focused wave groups -- Wave amplification -- Wave loads -- OpenFOAM®; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.112430
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Two or more marine structures deployed side by side may encounter strong water-body resonances within narrow gaps between them. It may cause significant wave loads on structures and the green water phenomenon on the deck. In this article, the transient fluid motion within a narrow gap formed by two fixed boxes suffered from incident focused wave groups is investigated using a two-dimensional viscous flow numerical wave flume. The focused wave groups adopted have the spectral peak frequency equal to half the fluid resonant frequency inside the gap. The wave fields both inside the gap and around the two-box system, the response/damping time of the transient wave surfaces inside the gap, the maximum wave forces and the ratios of the 2nd-order to the corresponding 1st-order wave surfaces/forces are investigated. It is revealed that the most dangerous place to green water is always the front edge of the two-box system. The damping time of the 2nd-order wave surface is significantly larger than that of the 1st-order one. As the incident wave amplitude rises, the ratios of the 2nd-order to the first-order wave surfaces/forces becomes increases gradually and can even exceed 100% for the wave surface, the horizontal wave force and the moment. Highlights: Second-order transient gap resonance between two fixed boxes induced by focused wave groups is simulated based on OpenFOAM®. Four different physical quantities related to the hydrodynamics of the transient gap resonance are systematically studied. The four physical quantities include: (1) wave elevations in the gap and around the two-box system, (2) horizontal wave forces, (3) vertical wave forces and (4) wave moments. The relative importance of high-order harmonic components is comprehensively discussed for all the four physical quantities. Both the response time and the damping time for the lowest two order wave elevations in the gap are also studied in detail.