Numerical Study of Long-Period Infragravity Wave on the Nearshore of Dongsha Island

View Statistics Email Alert RSS Feed

Information

Details

Project title

Code/計畫編號

MOST105-2221-E032-038-MY2

Translated Name/計畫中文名

東沙環礁水動力與海岸地形變遷之研究-東沙島近岸長週期亞重力波之數值研究

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=11883339

Year

2016

Start date/計畫起

01-08-2016

Expected Completion/計畫迄

31-07-2017

Bugetid/研究經費

893千元

ResearchField/研究領域

土木水利工程

東沙島位於南中國海東沙環礁西侧，是一個露出海面可居住的島嶼。由於位處颱風經常過境區域，沙灘易受到嚴重侵蝕，故1996年設置了突堤和離岸堤之海岸保護工程，雖然減緩侵蝕現象，但島嶼西侧礁盤上隨季節性流場變化而擺動的沙嘴景觀，卻受水流改變而逐漸消失。亞重力波被觀測到是珊瑚礁環境的主要成分波，其能量會在颱風伴隨高水位的情況下顯著增強，它會引起長週期震盪而增加海岸沙灘沖刷。此外，島上規劃建設泊船碼頭，但亞重力波之長週期震盪會導致港池共振，導致船隻無法靠泊，為了詳細暸解這些物理過程，本計晝利用根據Boussinesq方程式之非線性波浪模式，以二維平面水工試驗驗證後，將描述島嶼近岸亞重力波運動與波浪溯上特性，並考慮礁底床為海草之摩擦效應。模式結果將提供颱風緊急應變規劃、颱風波浪侵蝕率及港池發生震盪之風險評估。 Dongsha Island, located at the western of the Dongsha Atoll in the South China Sea, is an inhabited coral reef island. Due to the geographic location on the regular path of typhoon, coastline has suffered severe erosion. In 1996, groins and offshore breakwaters were built around the island to prevent the shoreline change. However, the engineering constructions redistributed the characteristics of hydrodynamics and resulted in the disappearance of seasonal sediment movements at the east of the island, which is the famous landscape in Dongsha. Infragravity waves have been found to be the dominant wave components on reefs. The energy dramatically amplifies during typhoon events with high tide. The strong resonant oscillations would significantly enhance the beach overwash. Additionally, a boating harbor is considered to build on the reef. Infragravity oscillation can cause disturbances inside the harbor. To understand the complex wave transformation processes over the reef, a fully nonlinear wave model based on Boussinesq equations, validated using a 2-D reef laboratory data, will be used to describe the infragravity motion and runup. Influence of the vegetation bottom on the hydrodynamic processes will be investigated as well. This model study will provide for typhoon-emergency planning, typhoon-induced erosion rate and the harbor at risk of long-period oscillations.

DSpace CRIS

Numerical Study of Long-Period Infragravity Wave on the Nearshore of Dongsha Island

Details

Description