Numerical Modeling of Long-Period Infragravity Waves in Harbors and an River Mouth

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Project title

Code/計畫編號

MOST109-2221-E032-020

Translated Name/計畫中文名

長週期亞重力波於港灣及河口海岸之數值模擬

Project Coordinator/計畫主持人

Shih-Feng Su

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Water Resources and Environmental Engineering Tamkang University

Website

https://www.grb.gov.tw/search/planDetail?id=13526864

Year

2020

Start date/計畫起

01-08-2020

Expected Completion/計畫迄

31-07-2021

Bugetid/研究經費

856千元

ResearchField/研究領域

土木水利工程

長週期亞重力波之波動對於沙灘海岸環境是重要的水動力，亞重力波動會引起向離岸、沿岸傳輸及離岸流，暴風與颱風等事件會形成更高能量，對於海岸的衝擊更甚於短週期之風湧浪。此外，溯上、沖刷及越波等侵蝕沙丘與離岸沙洲，了解此波浪基本特性可建立近岸地形與岸線穩定的地貌型態。港灣、珊瑚礁海岸及潮口等處是近年關心的區域，位在台灣東岸花蓮港和蘇澳港，在颱風期間存在港池水位振盪的問題，靜穩度影響船舶繫纜安全。太平島碼頭與規劃中的東沙島港灣位在珊瑚礁環境，受到珊瑚礁地形增強之亞重力波可能增強港內振盪。本計劃利用布氏數值模式FUNWAVE-TVD及高解析網格模擬長週期波浪，並和港內實際觀測值比對藉以了解水動力物理特性。另外，本研究計畫利用模式與觀測建立曾文溪河口長週期亞重力波與輸沙之關係並評估防洪影響性。 Motions of long-period infragravity waves are substantial hydrodynamics on gently sloping coasts. They include cross-shore leaky waves and alongshore edge waves, and modulate rip currents, which have a large range of implications in the sedimentary dynamics on coastal zones. Under storm and typhoon events, nearshore infragravity energy are higher than wind-generated short waves. The wave motions can induce runup, overwash and overtopping, which eventually promote dune erosion and barrier breaching. Understanding characteristics of infragravity waves will provide a great assessment of coastal morphodynamics and shoreline changes. Harbors, coral reefs and tidal inlets have received attentions in recent years. Infragravity waves within harbors can be amplified by resonance and induce large seiches. Hualien and Suao Harbors at the eastern of Taiwan frequently suffer considerable harbor oscillations during typhoon conditions. On coral reefs, long waves in harbors of Taiping and Dongsha Island can be firstly amplified by reef morphology. Therefore, the aim of the study is to apply Boussinesq-type model, FUNWAVE-TVD, to predict infragravity waves on the coastal zones with harbors. Model simulations with field measurements would provide assessments of spatial variation of long-period waves. In addition, the measured sediment accretion at the inlet occurred during energetic waves. The model simulations could evaluate the role of infragravity waves in the sedimentary dynamics of wave-dominated Zengwen river mouth.

Keyword(s)

亞重力波
布氏模式
港池振盪
河口
infragravity waves
Boussinesq modeling
harbor oscillation
river mouth

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Numerical Modeling of Long-Period Infragravity Waves in Harbors and an River Mouth

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