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| 研究生： |
阿维斯 Avicenna An-Nizhami |
|---|---|
| 論文名稱： |
使用直接施力沉浸邊界法於光滑粒子水動力模型中進行受力計算 Hydrodynamic loading calculation of smoothed particle hydrodynamics using direct forcing immersed boundary method |
| 指導教授： |
陳明志
Ming-Jyh Chern |
| 口試委員: |
林怡均
Yi-Jiun Peter LIN 朱佳仁 Chia-Ren Chu 張倉榮 Tsang-Jung Chang |
| 學位類別： |
碩士 Master |
| 系所名稱： |
工程學院 - 機械工程系 Department of Mechanical Engineering |
| 論文出版年： | 2016 |
| 畢業學年度： | 104 |
| 語文別： | 英文 |
| 論文頁數： | 80 |
| 中文關鍵詞： | 光滑粒子水動力法 、直接施力沈浸邊界法 、自由液面流 、流固耦合 |
| 外文關鍵詞： | Smoothed particle hydrodynamics, direct forcing Immersed boundary method, free surface flow, fluid-structure interaction |
| 相關次數： | 點閱：355 下載：4 |
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在光滑粒子水動力法(SPH)中,如果要計算固體受力必須沿著固體邊界進行應力積分。
但是由於SPH是由基於拉格朗日方法因此在計算應力時程序繁複困難,主要是因為需計算固體複雜邊界的法線方向與切線方向,因此本研究引入直接施力沈浸邊界法(DFIB)來計算SPH方法中的固體受力,藉此進行流固耦合的數值計算。相對於原來SPH方法需要進行邊界的應力積分,DFIB方法則只要把固體區域內的虛擬力量積分即可的固體的受力,不需要計算邊界的法線與切線方向,程序上較為簡潔易執行。為了驗證這個SPH-DFIB 方法,固定圓柱在一移動上板引致的穴流以及一移動圓柱在一封閉空間引起的流場用來 作為驗證例子。SPH-DFIB方法計算圓柱受力結果與其他方法或文獻相比具有一致性,因此可證明SPH-DFIB方法在計算固體受力的正確性。另外本SPH-DFIB方法也用於在一自由液面下的移動圓柱所引起的波浪與流場。計算結果顯示,流場型態可依圓柱附近的渦漩變化分為三個模態。同時可發現KC數對於圓柱受力有較為明顯的影響。
The common method to predict the hydrodynamic loading in Smoothed Particle Hydrodynamics (SPH) is the calculation of the surface integral. Because of the Lagrangian nature of the SPH, enforcing the non-slip boundary condition is a challenging task. In addition, calculation of the hydrodynamic force requires information of normal vector which is difficult to be obtained for moving body and complex geometry. To study the solid-fluid interaction and to calculate the hydrodynamic force, the direct forcing immersed boundary method (DFIB) is implemented to the SPH scheme. Instead of surface integration, DFIB method calculate the hydrodynamic force using volume integration. Flow past a cylinder in a lid-driven cavity and an oscillating cylinder in an enclosure at low Keulegan-Carpenter (KC) number are used as validation cases and the results obtained by the proposed SPH-DFIB method are compared with the benchmark results.The comparisons show that the proposed SPH-DFIB method is able to predict hydrodynamic loadings on a cylinder properly. The proposed method is applied to simulate an oscillating cylinder beneath a free surface in a quiescent fluid. Simulations are performed at various KC numbers and depth ratios. The flow patterns are divided into three modes according to the characteristic of wake around the cylinder, the number of vortices and vortex migration patterns. The results demonstrate that the effect of KC number is considerably larger than the depth of submergence on the in-line force. On the contrary, the transverse force and free surface elevation are more affected by depth of submergence, in particular at a low KC number.
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