波流作用下海岸漂砂量估算式之研究

A Study of the Sediment Transport Formula under Combined Wave and Current Conditions

林銘崇(Ming-Chung Lin) ； 江允智(Yun-Chih Chiang) ； 蕭松山(Sung-Shan Hsiao)

《海洋工程學刊》 9卷2期 (2009/12) Pp. 177-205

https://doi.org/10.6266/JCOE.2009.0902.04

摘要

對於海岸線及海岸地形變化之研究一般多以數值模式進行分析，而數值模式則依漂砂傳輸率配合地形資料以漂砂守恆方程式解析爲主，如何準確的計算海岸漂砂量應爲最重要之基礎。目前國內從事海岸地形變化之數值模式中有關海岸漂砂量估算模式，大多來自國外實驗室或現場觀測之經驗公式，各有其適用性且缺乏力學機制而無法完全適用台灣複雜且多變的海岸環境。本文擬改良既有同時包含波流機制的海岸漂砂量懸浮載與底床載估算式，參考Dibajnia & Watanabe提出基於近岸波浪向岸傳遞過程之不對稱性，將波峰及波谷作用半週期下之非穩定流藉由半週期平均之等效流速假設，轉爲擬穩定流之理論爲出發點，並將非線性波力學機制分別引入將相關參數公式化；分析過程中並引入沙漣的存在對海岸漂砂的影響，藉由前人對沙漣形成過程對流場的影響分析，將沙漣存在的底部邊界層範圍擴大至沙漣影響底部流場的範圍，期能建立符合力學機制及現場底床特性之漂砂量估算模式，提供海岸地形變遷數值模式漂砂量估算之應用。

關鍵字

海岸漂砂量 ； 不對稱性 ； 非線性因子 ； 沙漣

並列摘要

For the general purpose of morphodynamic simulations in coastal zone, a simple-based formula is usually employed to calculate sediment transport. A total load sediment transport formula based on recent studies on the bed load and suspended load transport for the model of coastal morphodynamic evolutions are presented. The cycle-mean net sediment transport rates are computed from the combined wave-current total bottom shear stress and the formula takes into account the velocity and acceleration asymmetries of the wave as they propagate towards the shore. The specification of the bed roughness is computed by grain related component, form drag component by sandy ripples and the sediment transport component, which is also included in the formula. A comparison has been carried out between the net sediment transport and experimental results for different wave-current conditions and the results are reasonable and accurate.

並列關鍵字

sediment transport rate ； asymmetry parameter ； nonlinear parameter ； sandy ripples