Published online by Cambridge University Press: 18 March 2019
Free surface oscillations in a narrow gap between elongated parallel bodies are studied numerically. As this represents both a highly resonant system and an arrangement of relevance to offshore operations, the nature of the damping is of primary interest, and has a critical role in determining the response. Previous experimental work has suggested that the damping could be attributed to laminar boundary layers; here our numerical wave tank successfully resolves both wave and boundary layer scales to provide strong numerical evidence in support of this conclusion. The simulations follow the experiments in using wave groups so that the computation is tractable, and both linear and second harmonic excitation of the gap are demonstrated.
Movie 1 (for mesh A3) shows the numerically computed free surface elevation around the boxes during passage of the incident transient wave group for Case A (in the region 2.5 m < x < 8.5 m, -4.0 m < y < 0 m, which is not the full extent of the NWT). Note that the vertical axis is stretched, such that 1 unit in the vertical = 5 units in the horizontal, to more clearly show the free surface motions. To this end, the boxes are shown as transparent.