Numerical Study of Wave Characteristics in Multiphase Irregular Breaking Waves Field

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Project title

Code/計畫編號

NSC97-2221-E236-011

Translated Name/計畫中文名

碎波帶內斜向高頻波與多方向不規則波交叉作用流場特性之研究

Project Coordinator/計畫主持人

Ruey-Syan Shih

Funding Organization/主管機關

National Science and Technology Center for Disaster Reduction

Department/Unit

Department of construction and spatial design, Tungnan University

Website

https://www.grb.gov.tw/search/planDetail?id=1696405

Year

2008

Start date/計畫起

01-08-2008

Expected Completion/計畫迄

31-07-2009

Bugetid/研究經費

444千元

ResearchField/研究領域

土木水利工程

本計劃擬應用以邊界元素法(BEM)所建立的二維模式斷面水槽及三維模式之數值多方向不規則蛇形造波水槽(serpent type wave generator)，配合時間領域、差分觀念來進行數值模擬，探討不規則波波動場與碎波後所產生的高頻率簡諧波(high frequency harmonic wave)交互作用下所產生的效應。海岸工程主要發生在近海淺水區，該區域也是波浪發生淺化、繞射、折射、碎波及反射等各種物理現象最錯綜複雜的地區，也是影響漂砂活動與海岸變遷等相關活動最主要的因素。本研究計畫主要以數值模擬及多方向不規則波為主，探討波浪在淺化過程，因發生碎波而使水面產生較高頻之擾動(surf beat and swash oscillation)，以反射波之形式返回大海，也會產生相對不同大小之沿岸流，產生斜向波交叉作用(cross-shore motion)，對不同方向之入射波的變形、能量衰減及碎波點與碎波臨界之影響程度不一，尤其在碎波帶內對因波浪發生碎波所產生的擾動現象對整個波動場、表層流及速度場等之影響，更會影響到漂砂與海岸變遷之評估。因此本計劃擬探討整個入、反射波浪之交互作用下複雜的三維流體運動模式，並以漸進之方式先由二維運動模式之驗證來更進一步逐步完成三維模式之建立、模擬、驗證與應用。本計劃擬分三年來逐步探討多方向不規則波浪所產生的波浪與波浪及波浪與地形之交互作用，以及交互作用下所產生的變形問題、速度場(velocity field)變化與水分子運動之軌跡(path line)或渦流等三維運動模式之研究。第一年將先利用2D 之水槽來探討對向波浪與入射波作用時之波形變化、速度場與水分子之運動軌跡，用來檢驗三維模式在斜向角度為零度時之模擬結果。第二年度將採用三維L 型數值多方向不規則造波水槽，假設為等水深之情況，探討入射波浪與其對向高頻波浪作用時之波形變化，速度場與水分子之三維運動軌跡，並探討斜向波(oblique wave)之斜向角度對入射波浪之影響。第三年計畫擬以第二年對兩側不同入射波與其對向高頻波浪交互作用之研究結果為基礎，配合任意海底地形之影響因素，考量地形變化或坡度對三維波動波形變化、三維波動速度場與水分子之三維運動軌跡結果之影響，並對多方向入射、反射波交互作用作整體影響之評估，尋找變化趨勢。 Is this project, we formulate a multiphase numerical model by using the BEM to the investigations of multi-directional irregular wave field, which incorporates the interaction between in coming wave and reflected wave as well as fluid and fluid phase. Coastal constructions are mostly located in the surf zone area, which is also a considerably complicate area of shoaling, diffraction, refraction, breaking, reflection…etc, wave breaking is one of the important process in the surf zone, which is also the main cause of many other process such as turbulence, transportation of surf zone and the movement of shoreline. The surf beats (wave breaking) in the surf zone is mainly the cause of the cross-shore motion, which also cause the generation of high frequency energy and hence transferred into harmonics waves, these various types of surf zone phenomena will be study accordingly. The development of two dimensional as well as three dimensional NWT will be adopted simultaneously in this study. The modeling of oscillations cause by surf beat and back swash will be carried out by the generation of multi-directional high frequency harmonic wave (multi-phase reflected wave) and/or high frequency irregular wave, to investigate the deformation of wave profile, wave field and particle path-line in three dimensional motions, which the cross-shore motion will be studied. Proceeding of this project would be last for three years. Formula derivation and the modeling of numerical scheme would be proceeding in the first year; the model will be verified by studying the case of multi-component regular and irregular wave generation, which incorporates not only the interaction between in coming wave and reflected wave, but also fluid and fluid phase. In the second year, we formulate representing interaction between in coming wave and reflected wave as well as fluid and fluid phase by using the 3D L-type multidirectional wave generator, and explore the cross shore motion of wave deformation, wave field, particle path-line, and wave-wave interaction in three dimensional motions. Finally, a slopping beach will be adopted in the model, the interaction between bottom topography, short wave and long wave in multi-direction is investigated.

Keyword(s)

邊界元素法
蛇形造波水槽
高頻率簡諧波
多向不規則波
波動場
Boundary element method
Serpent-type wave generator
High frequencyharmonic wave
Multi-directional irregular wave
Wave field

DSpace CRIS

Numerical Study of Wave Characteristics in Multiphase Irregular Breaking Waves Field

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