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Amplified exchange rate by tidal forcing of a piecewise-linear Helmholtz bay

机译：通过分段线性亥姆霍兹湾的潮汐强迫放大的汇率

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摘要

Sea-level and current measurements have been performed in the Mok Bay, a tidal embayment in the Dutch Wadden Sea, situated on the island of Texel, the Netherlands. Characteristic for this estuary is its nonuniform hypsometry. Oscillations in both water level and inflow of the estuary were observed, with characteristic frequencies of 31 and 48 cycles per day. The significant change in basin shape between low and high water is the cause for the existence of these two frequencies of resonance. Due to its semi-enclosed nature, the basin could at both tidal phases be characterized as a Helmholtz resonator, albeit of different dimensions. Depth measurements were performed to find these characteristic dimensions of the estuary, allowing the determination of its theoretical Helmholtz frequencies. These estimates match to within 10% with the observed frequencies, and this deviation can partly be explained. Although sea level oscillations at these frequencies have small amplitude (of order 1 cm), the accompanying oscillatory flow at the entrance is of similar magnitude as the tidal flow. The water level measurements (spanning only 8 days of data) were therefore modeled using a piecewise-uniform hypsometry that approximates the real hypsometric curve well. The simplified semi-analytical piecewise-linear viscous Helmholtz model captures the observed combination of tidal and eigenoscillations well. However, despite its simplicity, this model is able to display nonlinear behav- ior for certain parameter values. This is because of the intrinsic nonlinearity that accompanies the matching of the low and high water phases. In the setting studied here, bifurcations up to period 13 were found. This nonlinear type of response may be of importance in facilitating an extra exchange of sediments and nutrients between the Bay and the sea.
机译：已经在位于荷兰特克塞尔岛上的荷兰瓦登海的潮汐湾莫克湾进行了海平面和海流测量。该河口的特征是其非均匀的测压法。观察到水位和河口入水的振荡，每天的特征频率为31和48个周期。高水位和低水位之间盆地形状的显着变化是导致这两个共振频率存在的原因。由于其半封闭性质，该盆地在两个潮汐阶段均可被表征为亥姆霍兹共振器，尽管其尺寸不同。进行深度测量以找到河口的这些特征尺寸，从而确定其理论亥姆霍兹频率。这些估计值与观察到的频率匹配在10％以内，并且可以部分解释这种偏差。尽管在这些频率下的海平面振荡幅度较小（约为1厘米），但在入口处伴随的振荡流的大小与潮汐流的大小相似。因此，使用分段均一的测压法对水位测量值（仅涵盖8天的数据）进行建模，该测压法很好地逼近了实际的测压曲线。简化的半解析分段线性粘性亥姆霍兹模型很好地捕获了观察到的潮汐和本征振荡的组合。但是，尽管它很简单，但是该模型仍能够显示某些参数值的非线性行为。这是由于低水位相和高水位相匹配所固有的非线性。在这里研究的环境中，发现了直到周期13的分叉。这种非线性类型的响应对于促进海湾与海洋之间的沉积物和营养物的额外交换非常重要。

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  • 来源
    《Ocean Dynamics》 |2011年第12期|p.2061-2072|共12页
  • 作者

    J. P. de Boer; L. R. M. Maas;

  • 作者单位

    NIOZ Royal Netherlands Institute for Sea Research,P.O. Box 59,1790 AB, Den Burg, the Netherlands;

    NIOZ Royal Netherlands Institute for Sea Research,P.O. Box 59,1790 AB, Den Burg, the Netherlands;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    tides; estuary; eigenoscillation; chaos;

    机译：潮汐河口;本征振荡混沌;

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