本實驗目的為探討聲波振盪對管道流體的影響。以鼓風機作為氣源，氣流經由低速風洞，提供實驗所需之均勻流，待流經測試段，於下方利用喇叭產生聲波振盪，激擾出一脈衝流衝擊流體。利用函數產生器對喇叭送出不同頻率之訊號源，造成不同頻率之聲波振盪，配合不同流速，組合出多種流場情形並加以量測。實驗以熱線測速儀為主要量測儀器，經由量測所得之數據，進行管道中流體速度、頻率、擾亂度等的分析。實驗中的變動參數包括：所提供之均勻流風速，以及聲場的頻率和振幅。

    結果顯示，管道中流體經由聲波振盪後，激擾出的脈衝流衝擊流體後，流體所呈現的頻譜反應依隨著聲波的振動而改變，與均勻流流速無直接的關連性；在振動頻率90 Hz時頻譜能量達到極大值，其後頻率愈高能量愈低。振動頻率與頻譜能量並非呈線性關係。

    而受脈衝流衝擊後，管道中流體流速變化的結果顯示，流體在脈衝流出口上方有加速情形，而在管道下游處有減速情形產生，且均勻流流速在3 m/s時，管道中流體速度變化情形最為明顯。當均勻流流速愈大，受脈衝流所造成的影響愈不明顯。

This thesis studied the influence of the acoustic excitation upon velocity distributions in a duct flow. A low-speed wind tunnel was used to create a laminar flow. An oscillating flow induced by sound wave from a speaker installed on the bottom wall of the test section was introduced to interact with the main flow. 

    Various sound wave frequencies and flow velocities were applied in the experiment. Velocity distributions, turbulent distributions were measured using Hot-Wire Anemometry. The controlling parameters included laminar flow velocity, sound wave frequency and sound wave amplitude.

    The results showed that the interaction of the tunnel flow and the pulse flow was affected by the frequency of the acoustic driver. The flow velocity was increased at the entrance of the pulse flow, but was decreased at down stream. The disturbance caused by the pulse flow was not obvious when main flow velocity was increased.

中文摘要	I
英文摘要	III
目錄	IV
圖目錄	VI
第一章 前言	1
1.1 研究動機	1
1.2 文獻回顧	2
1.2.1 聲波激擾之相關應用研究	2
1.2.2 粒子沈積之相關研究	3
第二章 實驗方法與設備	8
2.1 實驗設備	8
2.1.1 喇叭與訊號源	8
2.1.2 低速風洞	8
2.1.3 氣源	9
2.1.4 測試段	9
2.1.5 皮托管	9
2.1.6 熱線測速儀	10
2.1.7 類比訊號擷取卡	10
2.2 實驗參數	10
2.2.1 均勻流風速	10
2.2.2 聲波振盪頻率	11
2.2.3 喇叭振幅	11
2.2.4 量測範圍	12
2.3 實驗數據計算	13
2.3.1 流場擾動情形	13
2.3.2 流場速度	14
2.3.3 頻譜分析	16
第三章 結果與討論	17
3.1 速度分析	18
3.1.1 速度分析-無聲波激擾下改變風速	18
3.1.2 速度分析-流場為5 m/s下改變聲波激擾條件	18
3.1.3 速度分析-聲波頻率為90 Hz時改變流速	19
3.2 頻譜分析	21
3.2.1 頻譜分析-無聲波激擾下改變風速	21
3.2.2 頻譜分析-流場為5 m/s下改變聲波激擾條件	22
3.2.3 頻譜分析-聲波頻率為90Hz時改變流速	23
第四章 結論	25
4.1 速度分析結論	25
4.2 頻譜分析結論	26
第五章 未來方向	27
參考文獻	29
圖目錄
圖1 低速風洞..................................................................................................32
圖2 鼓風機與變頻器.....................................................................................33
圖3 測試段尺寸圖..........................................................................................34
圖4 皮托管......................................................................................................35
圖5 風速和鼓風機變頻器頻率關係圖.........................................................36
圖6 漸縮段尺寸圖..........................................................................................37
圖7 儀器配置圖..............................................................................................38
圖8 實驗流程圖..............................................................................................39
圖9 量測點方向定義圖.................................................................................40
圖10 風速3~9 m/s，聲波頻率0 Hz，X 方向速度與擾動量.....................41
圖11 風速5 m/s，聲波頻率0~270 Hz，X 方向速度與擾動量.................42
圖12 風速3~9 m/s，聲波頻率90 Hz，X 方向速度與擾動量...................43
圖13 放大電壓2V，風速3 m/s，聲波頻率90 Hz，XY 全平面量測，
X 方向速度與擾動量............................................................................44
圖14 放大電壓1V，風速3 m/s，聲波頻率90 Hz，XY 全平面量測，
X 方向速度與擾動量............................................................................45
圖15 聲波頻率0 Hz,風速(a)3 m/s,(b)5 m/s,(c)7 m/s,(d)9 m/s,頻率-頻譜
強度分析圖............................................................................................46
圖16 聲波頻率0 Hz,風速(a)3 m/s,(b)5 m/s,(c)7 m/s,(d)9 m/s,管道位置-
頻譜強度分析圖....................................................................................47
圖17 風速5 m/s,聲波頻率(a)0 Hz,(b)45 Hz,(c)90 Hz,(d)135 Hz,(e)180
Hz,(f)225 Hz,(g)270 Hz,頻率-頻譜強度分析圖..................................48
圖17 (續).........................................................................................................49
圖18 風速5 m/s,聲波頻率(a)0 Hz,(b)45 Hz,(c)90 Hz,(d)135 Hz,(e)180
Hz,(f)225 Hz,(g)270 Hz,管道位置-頻譜強度分析圖..........................50
圖18 (續).........................................................................................................51
圖19 聲波頻率90 Hz,風速(a)3 m/s,(b)5 m/s,(c)7 m/s,(d)9 m/s,頻率-頻
譜強度分析圖........................................................................................52
圖20 聲波頻率180 Hz,風速(a)3 m/s,(b)5 m/s,(c)7 m/s,(d)9 m/s,管道位
置-頻譜強度分析圖..............................................................................53

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