| 中文摘要 |
本論文採用計算流體力學的方法，探討均勻流通過軸對稱體的流場特性，我們所研究的幾何外型為系列58中編號4154-4159的六個軸對稱潛體。在本研究中，我們採用不同近壁區網格密度、不同紊流模型，來進行軸對稱旋轉體穩態流場計算，雷諾數設定為20 × 10^6。網格的設計是以結構性網格包覆潛體，外側再以非結構性網格作空間分割，其中近壁區網格分為四種情況，最接近壁面的網格寬度分別為y^+ = 1、20、30、100；紊流模型則有三種，分別為標準k-ε模型、帶旋流修正的k-ε模型（realizable k-ε model）、以及剪切應力傳輸k-ω模型（SST k-ω model）。我們比較上述各種組合下的計算結果，包括阻力、邊界層的發展等，其中阻力部分也與實驗數值進行比對。我們發現，在相同的網格下，不同的紊流模型對於不同胖瘦程度的潛體形狀會有不同的效應，對於比較短胖的潛體形狀，標準k-ε模型所得之阻力有較小的誤差，而對於較瘦長的潛體形狀，另外兩者會有較佳的阻力預測。
The present study investigated a uniform flow past a body of revolution by the CFD approach. Of particular interest in our study are the DTMB Series 58 Model 4154-5149 forms. We employed meshes of different density (with y^+ = 1, 20, 30, and 100, respectively) and several turbulence models (standard k-ε model, realizable k-ε model, shear-stress transport k-ω model) to conduct a series of computations at the Reynolds number 20 × 10^6. For each computation, a thin layer of structured grid was employed on the body surface and an unstructured grid was then generated outside the structured one. We compared the computed results which includes the resistances and boundary layer developments. Part of the results were also compared to available experimental data. It was found that under the same grid, different turbulence models created different effects on bodies of different slenderness ratios. For a body with a smaller slenderness ratio, the standard k-ε model leads to a better resistance prediction than the other two models. However, as the slenderness ratio is increased, the other two models have a better performance in resistance prediction than the standard k-ε model. |
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