浅滩影响下的近岸低频波浪研究

Study on infragravity waves over a nearshore shoal

周期在25～300 s之间的低频波浪对海岸附近的泥沙输运、港内水面波动和泊稳等都有重要影响。虽然针对低频波浪的理论研究已有较多成果,但是结合实际工程针对浅滩上低频波浪的研究较少。采用非静压波浪模型SWASH对浅滩上波浪进行数值模拟,并对时域水面结果进行长短波分离,探讨低频波浪在浅滩上的演变规律。模拟结果显示,浅滩上低频波浪主要由约束长波和自由长波组成,约束长波占主要部分;低频波浪的能量来自于短波波群能量的转化;低频波浪能量增长率与h^(-5/2)成正比;不同水文条件下浅滩对低频波浪演变和近岸低频波浪运动的影响具有一定规律性。

Infragravity IG waves with periods of 25~300 s have significant influence on sediment transport and can permeate into the harbors basin and consequently worsen the mooring conditions. Many theoretical studies focus on the resonance induced by IG waves in harbors, but few of them concerns the effect of shoal on the spatial propagation of IG waves nearshore especially combined with a practical harbor project. The present study systematically studies the influence of shoal on the propagation of IG waves by decomposing the series of water surface elevation obtained using the non-hydrostatic wave model SWASH. According to the results of simulation, the IG waves on the shoal are composed of the bound waves and the free waves with the bound waves being the main components. The energy is transferred from the wave group to the bound wave. IG wave component shows a growth rate close to the equilibrium response (∝ h -5/2 ). Under different hydrological conditions, the IG waves have regularity in the evolution process.