A two-dimensional (2D) viscous numerical wave flume is developed based on OpenFOAM® to investigate the transient gap resonance problem triggered by nonlinear focused wave groups. The narrow gap is formed by two closely-spaced boxes, where the weather-side box is allowed to heave freely under wave actions, but the rear one is firmly fixed. The overset mesh method is introduced in the numerical model to capture the weather-side box's large-amplitude motion accurately. This work mainly focuses on the coupled effects of free-surface nonlinearity and heave-freedom of the weather-side box on the fluid oscillations in the gap and heave motions of the weather-side box. The heave-freedom of the weather-side box is demonstrated to play an important effect on the period in which the maximum value of non-dimensional amplitude of fluid oscillation in the gap occurs. It is revealed that the free-surface nonlinearity significantly affects the nonlinear fluid oscillations in the gap but has a limited effect on the heave motions of the weather-side box. The four-phase combination method is further employed to conduct the higher harmonic component analysis to clarify the effects of higher harmonic components on the nonlinear response of fluid and box.

中文翻译：

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非线性聚焦波群触发的两个紧密间隔的盒子之间的瞬态间隙共振

基于 OpenFOAM® 开发了二维 (2D) 粘性数值波水槽，用于研究非线性聚焦波群引发的瞬态间隙共振问题。狭窄的间隙由两个紧密间隔的盒子形成，其中迎风侧的盒子可以在波浪作用下自由起伏，但后面的盒子被牢固地固定。数值模型中引入重叠网格方法，准确捕捉气象侧箱体的大振幅运动。本工作主要研究迎风侧箱体自由面非线性和升沉自由度对迎风侧箱体间隙中流体振荡和升沉运动的耦合影响。证明了迎风侧箱体的升沉自由度对间隙中流体振荡无量纲振幅最大值出现的时期具有重要影响。结果表明，自由表面非线性对间隙中的非线性流体振荡有显着影响，但对迎风侧箱体的升沉运动影响有限。进一步采用四相组合法进行高次谐波分量分析，阐明高次谐波分量对流体和箱体非线性响应的影响。