Numerical Simulation of Flow and Heat Transfer Characteristics in the Channel with a Transversely Oscillating Heated Circular Cylinder

本研究利用數值方法探討渠道內橫向振動加熱圓柱對流場與熱傳特性影響，數值方面是採用ALE 運動描述法來處理流體與固體介面相互影響的問題，並使用寬頻元素法配合非結構性網格加以分析。首先針對不同的振動振幅、振動頻率、雷諾數和阻塞比參數，分析渠道內橫向振動圓柱對尾流場渦漩形態的影響；進而探討渠道內橫向振動加熱圓柱的熱傳特性。研究結果得知，圓柱尾流場的渦漩形態，會受到振動頻率和振幅的影響，產生不同的渦漩形態，而阻塞比會使流場渦漩形態的轉變延遲發生；在圓柱熱傳效率部份，高振幅和高阻塞比的條件會讓渠道內流場的鎖頻區範圍增加，當渠道內流場發生鎖頻現象時，能夠有效增加流體的擾動，提升圓柱的熱傳效率。The study investigates the flow and heat transfer characteristics in the channel with a transversely oscillating heated circular cylinder. The variations of flow and thermal fields are classified into a class of moving boundary problems. In the numerical analysis, a spectral element formulation with arbitrary Langrangian-Eulerian method is adopted to solve the flow and thermal fields for moving boundary problem. The subsequent developments of the vortex shedding and heat transfer characteristics around the heat cylinders are presented in detail. The effect of Reynolds number, oscillating amplitude, oscillating frequency, blockage ratio on the flow structures and heat transfer characteristics of the heated cylinder are examined. The results show that the interaction between the oscillating cylinder and vortex shedding from the cylinder dominates the state of the wake. This phenomenon would disturb the flow and thermal fields in the channel flow and the heat transfer rate in the channel would be enhanced. Furthermore, as the flow and thermal fields may approach a periodic state in lock-in regime. The heat transfer of the cylinder in the lock-in regine is enhanced remarkably.誌謝.................................................i要................................................iibstract...........................................iii錄................................................iv目錄..............................................vi目錄..............................................xi號說明...........................................xii一章 緒論..........................................1.1 研究動機.........................................1.2 文獻回顧.........................................2.2.1 圓柱流場渦漩形態...............................2.2.2 加熱圓柱流場 ...................................3.2.3 寬頻元素法.....................................4.2.4 動態網格.......................................6.3 分步驟法.........................................7.4 研究目的與內容 ...................................8二章 物理模型及數值方法...........................10.1 物理模型........................................10.2 統御方程式與邊界條件............................10.3 數值方法........................................12.3.1 時間離散化....................................12.3.1.1 混合剛性穩定法(Mixed stiffly stable scheme).12.3.1.2 高階分步驟法(High-order Splitting Scheme)...13.3.2 空間離散化....................................15.3.3 ALE(Arbitrary Lagrangian-Eulerian)描述法......15三章 數值方法之驗證...............................20.1 穩態溫度流場的驗證..............................20.2 暫態溫度流場的驗證..............................21.3 溫度流場加入動態網格的驗證......................22四章 實例測試與驗證...............................26.1 格點獨立測試....................................26.2 加熱圓柱流場與其他研究結果比較..................27五章 渠道內橫向振動圓柱尾流渦漩之探討.............34.1 圓柱振動頻率對流場渦漩形態之影響................34.1.1 圓柱近尾流場探討..............................34.1.2 圓柱遠尾流場探討..............................35.2 圓柱阻塞比對流場渦漩形態之影響..................36.3 結論............................................39六章 渠道內振動加熱圓柱熱傳特性之研究.............63.1 圓柱振動對流場與溫度場的影響....................63.2 圓柱振動頻率對熱傳效率之影響....................64.3 圓柱阻塞比對熱傳效率之影響......................67.4 結論............................................68七章 結論與建議...................................91.1 總結............................................91.2 建議與未來展望..................................93考文獻............................................9