河口湾动力响应特征

Dynamic Responses in Estuaries:A Theoretical Analysis

一个等水深、湾宽线性变化的半封闭河口湾动力响应模式揭示了在外海潮动力及低频沿岸波动和风场作用下,河口湾响应场的一般特征。结果表明,底摩擦系数、水深、弯宽变化等参数与河口湾响应场之间的关系实质上反映了特定条件下河口湾动力波动场的能量集聚、转化和耗散机制。比较发现,河口湾潮响应场与低频响应场之间存在明显特征差异。当周期T>2d时,底摩擦效应不再重要。由此而提出的一个更为简化的河口湾低频响应模式使得低频响应特征更为直观和明确。此外,利用模式解,本文导出了河口湾共振的一般条件,并讨论了河口湾固有共振频率与湾宽变化及水深的关系。

A simple model is developed to interview the general features of the estuarine responses induced both by ocean tides and by low-frequency coastal fluctuations and wind forcings. Model estuary is assumed theoretically with constant depths and linearly varying breadth. Results indicate that the effects of the different bottom friction coefficient, the water depth adn the breadth variation parameter on the estuarine response field virtually reflect the difference of the energy accumulation, transformation and dissipation in estuaries. It is found by comparison that there are obvious differences between tide-induced and low-frequency forcing induced estuarine variations. For tide response, bottom friction is the very important factor to affect the response magnitude, while for low-frequency response the effect of the bottom friction became negligible. Thus a more simplified low-frequency estuarine response model is produced, which gives more straightformward view to the response characteristics, Moreover, from the model solutions we deduce a general requirement for estuarine resonance and discuss the relation between the resonance frequency and the estuarine breadth and water depth.