深水碎波衝擊直立壁之流場分析研究

Flow field measurement of deep water breaking wave impact on a vertical wall

趙偉廷(Wei-Ting Chao)

指導教授 ： 丁肇隆 ； 林銘崇

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00341

摘要

本文利用粒子影像測速儀(P.I.V.)並搭配影像接圖技巧，以線性變頻造波方式，製造深水碎波衝擊直立壁，研究碎波前後直立壁週遭流場所產生之變化。本研究僅著重在實驗結果所呈現物理現象的變化情況，作一定性上的探討。其中包含速度向量場之分析、渦度場之分析與壓力場估算等三項。從結果中可以看出，Plunging碎波在速度向量、渦度場以及壓力場，量測的結果都較Spilling碎波的結果大，因為Plunging碎波過程中，氣墊效應(air cushion)較Spilling碎波劇烈。從實驗結果可知，在Spilling與Plunging碎波時，波峰處會產生渦旋，衝擊直立壁後，因退水的緣故，渦旋會被向下帶離流場觀測範圍。利用堤前量測之速度場與控制體積動量守恆法，可以得到Spilling與Plunging碎波衝擊直立堤壁的瞬間，其自由液面下壓力分佈的結果近似對數曲線，與Kirkgoz(1995)利用壓力計量測的結果相似。

關鍵字

粒子影像測速儀；直立壁；壓力場估算；速度場 ； 渦旋場

並列摘要

Deep water breaking impact on a vertical wall were investigated in this research. The breaking waves were generated by linearly-varying-frequency wave trains. A P.I.V. measurement system was used to record the particle motion in fluids, such that the instantaneous wave flow field can be calculated. Based on the measured results, qualitative descriptions of the variations of flow field around the vertical wall during breaking wave impact process were made in this research. It showed that due to a plunging breaker causes much more violated flow filed than a spilling breaker does an air bag entrapped during the plunging breaking process. At wave crest, a vortex generation was produced during breaking processes. After wave impacting on a vertical wall, water recedes and the mores with water, then leaves the region of the vortex measured flow filed.
Using the measured velocity information near the vertical wall and the method of linear momentum conservation in a control volume, the pressure distribution on the vertical wall were calculated and distributed as a log law curve for spilling and plunging breaker cases. The obtained result was similar to the results obtained by Kirkgoz (1995) using pressure gauges measurements.

並列關鍵字

PIV measurement system , pressure field, velocity filed and vorticity filed, vertical wall

參考文獻

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