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題名 | 低雷諾數k-ε模式中之紊流尺度極限探討=Limit of Eddy length Scales in Use of Low-Reynolds-Number k-ε Models |
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作者 | 張克勤; 徐明君; Chang, Keh-chin; Shyu, Ming-juin; |
期刊 | 力學 |
出版日期 | 20001200 |
卷期 | 16:2 2000.12[民89.12] |
頁次 | 頁109-118 |
分類號 | 447.55 |
語文 | chi |
關鍵詞 | 紊流次層; 紊流尺度; Kolmogorov scale; Viscous sublayer; Eddy length scale; |
中文摘要 | 相關的文獻指出,紊流的尺度大致可分為兩個區域;遠離邊牆的區域,紊流尺度 是由流場的尺度所主導, 如外形尺寸和邊界層厚度等等; 而在近壁區且進入紊流次層( viscous sublayer )時, 流場的特性將會由 Kolmogorov scale (紊流中最小的尺度)所 主導。因而建議應在紊流的計算中,以 Kolmogorov scale 做為最小的下限尺度,並且認為 在紊流的尺度小於此下限後沒有紊流的存在。以此觀念重寫 Prandtl-Kolmogorov 關係式和 ε方程式,來解決 f μ > 1 和ε方程式在壁上產生奇異性的問題。本文並且成功的以渠道 流和背向階梯流來測試所擬議紊流尺度設限的可行性。 |
英文摘要 | It is known that the turbulence scales are mainly controlled by the large-scale structures, such as the flow geometric configuration, boundary-layer thickness, etc, away from the wall, while are characterized by the Kolmogorov scales (the smallest eddies in turbulence) within the viscous sublayer. Based on this observation, the Kolmogorov time scale is suggested to be the low bound of the turbulence time scale. Beyond the lower bound, there exist no eddies in this flow region. Following the above concepts, the Prandtl-Kolmogorov relation of the eddy viscosity and the ε transport equation are rewritten in order to avoid the unrealistic condition of f μ > 1 and the singularity occurring at the wall for the ε transport equation, respectively. It is shown, by the tests with the cases of channel flow and the cases of backward-facing step flow, that the above ideas are feasible. |
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