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題 名 | 控制橢圓噴流流場結構可能性之探討=Controlled Flow Structures of an Elliptic under Suitable Excitations |
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作 者 | 林源堂; 劉明山; 張益林; | 書刊名 | 逢甲學報 |
卷 期 | 31 1997.06[民86.06] |
頁 次 | 頁117-128 |
分類號 | 446.11 |
關鍵詞 | 不穩定模態演進; 模擬各處同時激發; Instability modes evolution; Pseudolocal excitation; |
語 文 | 中文(Chinese) |
中文摘要 | 本文以流場觀測驗證橢圓噴流在基本頻率和次諧和頻率聲波激發下之定量分析結果 ,並探討控制橢圓噴流流場結構之可能性。 比較不同頻率聲波激發對橢圓噴流動量傳遞之影響,發現基本頻率聲波激發f (f f ) 可加 強長軸方向之渦流形成,以增加橢圓噴流長軸方向上游之動量傳遞。次諧和頻率聲波激發 f (f /2,f /2)在短軸方向產生次諧和共振,可使渦流結合更結構化,顯著增加橢圓噴流短 軸方向動量傳遞。尤其當分別在長、短軸面同時施加基本頻率與次諧和頻率聲波激發f (f /2,f /2)或稱模擬各處同時激發,長軸方向渦流形成與短軸方向渦流配對發生於下游相同位 置z/a=1.5 ,短軸面可同時由外界和長軸面引進質量,很顯著增進短軸面之動量傳遞。流場觀 測之定性分析結果驗證模擬各處同時激發是最有效增進短軸方向動量傳遞的方法。 |
英文摘要 | The momentum transportation of an elliptic jet under acoustic excitations were investigated experimentally in this paper. Results indicate that the development of the unstable waves in the shear layer along the minor axis is faster than those in the shear layer along the major axis, therefore, the most unstable wave in the minor axis rolls up earlier than those in the major axis. It is interesting to find out that the vortex formation in the major axis occur almost at the same streamwise location as the vortex pairing in the minor axis, i.e., z/a=1.5. Consequently, such an elliptic jet excited by a fudamental frequency in the major-axis and a subharmonic frequency excitation in the minor-axis plane, i.e., f (f /2,f /2)can be said as the pseudolocally excited. Flow patterns show that the elliptic jet under pseudolocal excitation is the most effective approach to enhance the momentum transport in the minor-axis plane. |
本系統中英文摘要資訊取自各篇刊載內容。