Studies on Hydrodynamic and Air-flow Characteristics of a New Type of Wave Energy Absorber with Oscillating Water Column

本研究利用數值模擬及搭配水工模型試驗探討一新型波能擷取裝置之水動力與氣流特性。數值模擬係採用FLOW-3D流體動力軟體計算波能擷取裝置之波流場及風場變化，其中本研究選用one fluid計算模式分析流場特性及震盪水柱之波形變化，而風場則以two fluid計算模式模擬之。試驗方面係利用高速攝影機搭配雷射技術進行流場可視化拍攝。透過模擬與試驗結果比較，顯示模擬與試驗結果於流場、風場及水柱波形震盪特性相當一致。 經由研究結果顯示，裝置內水柱在震盪時將會壓縮空氣並於上方開孔處產生風速，當水柱水位上升時空氣將會自開孔流出；水位下降時空氣則會自開孔處吸入。由於新型裝置之水柱及波形變化相當穩定，因此裝置內受到水柱壓縮所產生的風速亦具有穩定之特性。本文探討不同波浪條件下，比較裝置所產生之風速及風能關係，由結果顯示，於不同波高條件下，當波高值越大其所能擷取之風能也越大，而在相同波高、不同相對水深d/L下，顯示隨著相對水深d/L的降低則有較高的擷取風能；相同波高且相同相對水深下，比較不同內氣室寬度與裝置體寬度比(b/B)，可得擷取風能即隨著b/B值的增加而有變大之特性。本研究進一步探討新型與傳統OWC裝置之差異，結果顯示本研究之波能擷取裝置有更佳的風能擷取表現。This paper presents a new type of wave energy absorber embodying OWC system, and discussing its hydrodynamics and air-flow characteristics. Using both computational fluid dynamics (CFD) and physical model tests in this study. A CFD called Flow-3D was employed, which one-fluid model is used to simulate the flow field of the oscillation of water column, and two-fluid model is adopted to simulate the wind field. The experimental tests measured the oscillation of water column and used the high speed camera with laser system to do flow visualization. The results show that the simulations of the flow field, the wind field and the free surface variation of the water column are quite constant and the same with the experimental tests. According to the results, when the water column of the air chamber oscillating by the waves, it will compress the air and generate the wind speed at the device. When the water column rise up it will cause the air flow out from the device, and flow in when it comes down. From the stabilization of water column variation, the wind speed caused by the water column will also be stabilize. The study adopted different wave definitions to discuss the relation between the wind speed and the wind power. The result shows the larger of the wave height induce the larger of the wind speed which it was generated and produced much more wind power in the different incident wave height conditions. In the same wave height but different relative depth conditions,the OWC device will absorber more wind power when the relative depth is decreasing. When the width of the air chamber b over the structure width B from OWC device is increasing,the OWC device will absorber more wind power in the same wave height and relative depth conditions. The study also compare with the conventional OWC,and the result shows that the present one absorber more wind power than the conventional one.目錄 摘要....................................................I Abstract...............................................II 目錄...................................................IV 表目錄................................................VII 圖目錄...............................................VIII 照片目錄................................................XI 符號說明...............................................XII 第一章...............................................緒論 1 1-1 研究背景...........................................1 1-2 文獻回顧...........................................2 1-3 研究目的...........................................5 1-4 研究方法...........................................7 1-5 本文架構...........................................8 第二章 數值模擬..........................................9 2-1 模擬流程...........................................9 2-2 控制方程式........................................11 2-3 RNG紊流傳輸模式...................................12 2-4 FLOW-3D使用之核心技術.............................13 2-4-1 流體體積法(Volume of Fluid, VOF)..........13 2-4-2 FAVOR(Fraction Area/Volume Obstacle representation)........................................14 2-5 模擬設定 .......................................15 2-5-1 模型建立..................................15 2-5-2 網格設置..................................17 2-5-3 邊界條件設定..............................20 2-5-4 模式選擇..................................21 2-5-5 求解設定..................................22 2-5-6 模擬條件..................................22 第三章 模型試驗.........................................25 3-1 試驗設備..........................................25 3-2 試驗流程..........................................29 3-3 試驗配置..........................................31 3-3-1 儀器架設..................................31 3-3-2 波高計率定................................35 3-3-3 試驗條件..................................36 3-4 試驗方法..........................................36 3-4-1 波形量測..................................36 3-4-2 流場可視化................................37 第四章 結果分析與討論....................................41 4-1 震盪水柱之波形變化.................................41 4-2 震盪水柱之波流場變化 ...............................43 4-3 氣室之風場變化....................................50 4-4 風能分析..........................................58 4-5 與傳統OWC比較.....................................70 4-5-1 傳統OWC波流場模擬分析......................70 4-5-2 傳統OWC風場模擬分析........................75 4-5-3 傳統OWC風能分析...........................79 4-6 紊流能量與紊流消散分析.............................81 4-7 渦度分析..........................................98 第五章 結論與建議.......................................107 5-1 結論............................................107 5-2 建議............................................108 參考文獻...............................................10