查詢結果分析
來源資料
頁籤選單縮合
題 名 | A Numerical Study on Turbulent Vortex-Shedding Flows Around a Cubical Form=流過方柱之紊流渦漩逸出流場數值研究 |
---|---|
作 者 | 彭逸凡; 黃榮鑑; | 書刊名 | 中國工程學刊 |
卷 期 | 22:5 1999.09[民88.09] |
頁 次 | 頁639-648 |
分類號 | 440.137 |
關鍵詞 | 紊流渦漩逸出; 大渦漩模擬法; 三維不穩定性效應; Turbulent vortex-shedding flows; Large eddy simulation; Three-dimensional instability; |
語 文 | 英文(English) |
中文摘要 | 本文以大渦漩模擬法(LES)解析流過方桂之紊流渦漩逸出流場;大渦漩模擬法中次 網格尺度 (SGS) 雷諾應力以渦漩黏滯模式模擬, 而其中伴隨的紊流渦漩黏滯係數則以 Smagorinsky 模式模擬; 流場計算結果的準確性藉由與實驗量測值的吻合度獲得驗證。本文 採用的 LES 法計算結果比傳統的二階閉合紊流模式計算結果更為準確, 能更加精確地預測 紊流渦漩之逸出頻率,以及方柱下游之速度分佈。本文計算結果顯示流過方柱之紊流逸出流 陽具有相當約三維性, Williamson 在實驗室中觀察到的三維不穩定性效應,即分佈於柱體 軸向的次渦漩,亦顯現於本文的數值結果中。方柱下游之三維渦漩由沿入流方向分佈的主渦 漩 (卡門渦漩 ) 及沿方柱軸向分佈的次渦漩構成。 次渦漩沿測向成對出現,成對渦漩結合 為 2.4D 的尺度規律分佈,使得主渦漩呈現波動狀。這些主渦漩、次渦漩的三維結構在尾流 近域附近相當清晰,往下游發展則快速破碎,在尾流遠域形成混亂的紊流渦漩。 |
英文摘要 | The turbulent vortex shedding flow behind a square cube is numerically analyzed by the LES approach. The eddy viscosity and Smagorinsky models have been used to simulate the SGS Reynolds stress and eddy viscosity, respectively. The performance of the computations is evaluated by comparing with available measurements, as well as with those results obtained from RANs. It is found that the LES approach predicts the Strouhal number and the mean stream-wise velocity profiles with a better accuracy than RANs. The present computational results reveal that the vortex shedding flow behind the square cube is quite three-dimensional. Williamson's experimental observation of mode B three-dimensional instability in the turbulent cylinder wake is numerically reproduced. The primary Karman vortices are found to be distributed along the full span of the channel in the near wake region, and are broken down quickly in the far wake region. Secondary vortices exist in pairs and are distributed along the span-wise direction with a wave-length of 2.4D. With the secondary vortices taking the form of waviness of the primary Karman vortices, the three-dimensional shedding vortices behind the cube are clearly illustrated. |
本系統中英文摘要資訊取自各篇刊載內容。