碎波拍擊直立壁之流場實驗量測

Abstract

本研究針對碎波之流場及其拍擊直立壁之鄰近區域進行量測，希望透過流場可視化之技術對拍擊過程的物理機制有進一步的了解。利用線性變頻之方式產生碎波，並使用粒子影像速度儀( Particle Image Velocimetry )量測碎波拍擊直立壁時之瞬時流場，比較有、無直立壁時碎波波形及其夾角的變化，並就各剖面之速度分佈進行探討。結果顯示當產生溢出型碎波時，碎波點之速度剖面分佈中在波峰上方1/3碎波波高之區域有向上線性遞增之垂向速度，越接近波峰其值越大，而當拍擊直立壁時，水平速度減低而向上之垂直速度增加，大致上在水深方向呈線性之趨勢。

Breaking-wave flow field and the flow field in the vicinity of breaking wave impact on a vertical wall are investigated in this research. Also, it’s anticipated that the knowledge of the mechanism of breaking wave impact on coastal structures can be improved through the flow visualization of impact process. Breaking waves are generated by a linearly-varying frequency wave train. Particle image velocimetry is used to measure the instant flow field of breaking-wave impacts. The comparisons of waveforms with and without a vertical wall will be made to see the differences of the wave crest angles. The each sectional speed is distributed and carried on the discussion. The result shows that when produce spilling breaking waves, the speed profile of above 1/3 wave height area has a linear increasing upward speed. When spilling breaking waves impact on a vertical wall, the speed profile indicates that the horizontal speed decreases and the upward vertical speed increases, and presents the linear trend along the direction of depth of water.