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Publications
Li, Y., Zhao, XL., Zou, Q.P., Milne, I.A., Geng, J. and Guedes Soares, C. (2024), Viscous and nonlinear effects on Helmholtz resonance in a gap induced by waves, Applied Ocean Research, Vol. 151, 104161
In the paper, the viscous and nonlinear effects on the gap resonance between a deep draught hull and a vertical wall, is investigated with special attention to low-frequency response, i.e., Helmholtz resonance. The OpenFOAM viscous-flow model results indicate that the gap response initially increases and then decreases with an increasing hull draft-to-depth ratio 0.4 < d/h < 0.98. Severe wave energy dissipation and very little wave reflection (i.e., Kd = 0.99, Kr = 0.07) are observed for specific hull drafts during gap resonance. In contrast, the potential-flow semi-analytical solution predicts the gap response increases monotonically with an increasing draft. It is found that a significant flow blockage occurs when the hull bottom approaches the seabed, weakening the gap resonance. The underlying mechanism is that although the vortices can be generated at the hull edge, the narrow water passage between the hull and seabed and the enhanced viscous effect prevent the full development of these vortices and water transport in and out of the gap. These underdeveloped vortices, in turn, hinder the transport of water particles and energy dissipation. Furthermore, numerical simulations at various incident wave heights (Hi) have shown that during Helmholtz resonance, characterised by low-frequency responses for d/h = 0.8, wave absorption performance is insensitive to Hi. This finding contrasts with the behaviour observed in traditional gap problems.
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