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研究生:賴佳聖
研究生(外文):Chia-Sheng Lai
論文名稱:排放角度與邊牆效應對浮昇射流影響之實驗研究
論文名稱(外文):An experimental study of discharge angle and boundary effect on buoyant jets
指導教授:朱佳仁朱佳仁引用關係
指導教授(外文):Chu, C.R.
學位類別:碩士
校院名稱:國立中央大學
系所名稱:土木工程研究所
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:英文
論文頁數:83
中文關鍵詞:孔氏效應浮昇射流
外文關鍵詞:Coanda effectAttachment
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摘 要
本研究以實驗方式來探討排放角度和底床邊界對單管浮昇射流之影響。實驗在一靜止的水槽中以台車拖曳排放鹽水的射流管來模擬橫向流場中的浮昇射流,實驗採用雷射引致螢光法配合CCD攝影機以連續擷取射流之影像,經由影像處理可得射流的軌跡和濃度場。實驗結果顯示:在無邊牆效應、有橫向流的狀況下,於同一下游距離,排放角度愈大,則射流的稀釋率會愈大。當豎管接近底床時,角度變化是否產生附著現象,由排放角度與豎管高度決定。若排放角度 時,附著現象便會發生,然而散佈係數會隨著橫向流流速的增加而變小。當附著現象發生時,邊界會抑制浮昇射流的混合,導致射流的稀釋情形變差。實驗結果並與美國環保署所發展之模式CORMIX比較,發現該模式無法準確地預測邊界效應及附著現象的稀釋情形。本研究之結果可供設計海洋放流管的排放角度參考。


Abstract
An experimental study of discharge angle and boundary effect on buoyant jets is presented. The experimental setup comprises a towed single jet discharging salt water into a laboratory tank with a horizontal plexiglass plate close to the diffuser port. Trajectories and concentration distributions of buoyant jets were measured by the planner laser-induced fluorescence (PLIF) method. It was found, due to the Coanda effect, buoyant jets will cling to the boundary when discharge angle , where β is the spreading coefficient. This phenomenon has a marked effect on the jet trajectory and its near-field dilution. Results of this study also showed that the near-field model CORMIX fails to predict above phenomenon.


目 錄
頁次
中文摘要Ⅰ
英文摘要Ⅱ
目錄Ⅲ
圖目錄Ⅴ
表目錄Ⅶ
符號表Ⅷ
第一章  簡介1
 1.1  緒言1
 1.2  研究目的3
 1.3  大綱3
第二章  理論基礎與文獻回顧5
 2.1  浮昇射流5
  2.1.1  一般特性5
  2.1.2  斷面積分6
 2.2  長度尺度7
 2.3  邊牆射流9
 
第三章  實驗設備與方法20
 3.1  實驗設備20
 3.2  影像擷取與流況觀測22
 3.3  雷射引致螢光法23
 3.4  實驗步驟25
第四章  結果與討論35
 4.1  無邊牆效應、無橫向流下改變角度之流況35
  4.1.1  射流軌跡36
4.1.2  稀釋率37
4.2  無邊牆效應、有橫向流38
  4.2.1  射流軌跡38
4.2.2  稀釋率39
4.3  無邊牆效應、有橫向流40
  4.1.1  射流軌跡41
4.1.2  稀釋率42
第五章  結論與建議78
 5.1  結論78
 5.2  建議79
參考文獻81
圖目錄
頁次
圖2.1 無橫向流之浮昇射流示意圖14
圖2.2 橫向流中浮昇射流欴軌跡圖15
圖2.3 浮昇射流長度尺度示意圖16
圖2.4 邊牆射流示意圖17
圖2.5 孔氏效應下之浮昇射流斷面受力示意圖18
圖2.6 豎管高度與排放角度之示意圖19
圖3.1 實驗設備配置示意圖26
圖3.2 馬達轉速電壓值與台車速度之關係圖27
圖3.3 流量計之讀數與真實流量之校正圖28
圖3.4 實驗配置圖29
圖3.5 雷射引致螢光法校正水箱配置示意圖30
圖3.6 螢光濃度與影像灰階值之關係圖31
圖3.7 不同螢光溶液濃度時雷射強度隨水深變化圖32
圖3.8 瞬時影像與時間平均影像比較圖33
圖3.9 雷射引致螢光法與CORMIX之比較圖34
圖4.1 在靜止水體中,雷諾數對純射流稀釋率的影響48
圖4.2 在ho/D = 20下,不同角度、不同Fo於靜止水體的軌跡變化圖49
圖4.3 在靜止水體中,水平排放(θ = 0)之軌跡變化圖50
圖4.4 在靜止水體中,水平排放(θ = 0)之射流寬度變化圖51
圖4.5 於靜止水體中,h0/D = 20的稀釋率變化圖52
圖4.6 於靜止水體中,h0/D = 20的稀釋率比較圖54
圖4.7 不同之密差福祿數(Fo = 25, 62)於ua = 2 cm/s的軌跡變化圖55
圖4.8 不同之密差福祿數(Fo = 25, 62)於ua = 4 cm/s的軌跡變化圖56
圖4.9 不同之密差福祿數(Fo = 25, 62)於ua = 8 cm/s的軌跡變化圖57
圖4.10 排放角度、密差福祿數和橫向流速對射流軌軌跡的影響58
圖4.11 排放角度、密差福祿數和橫向流速對射流軌軌跡的影響59
圖4.12 在ho/D = 20,ua = 2 cm/s中的稀釋率變化圖60
圖4.13 在ho/D = 20,ua = 4 cm/s中的稀釋率變化圖62
圖4.14 在ho/D = 20,ua = 8 cm/s中的稀釋率變化圖64
圖4.15 在不同橫向流下,不同角度所得之稀釋率變化圖66
圖4.16 在不同橫向流下,不同角度所得之稀釋率變化圖67
圖4.17 無邊牆效應與靜止水體中,F0 = 25,不同角度之射流等濃度圖68
圖4.18 邊牆效應與靜止水體中,F0 = 25,不同角度之射流等濃度圖69
圖4.19 邊牆效應與靜止水體中,F0 = 62,不同角度之射流等濃度圖70
圖4.20 ho/D=1,ua = 2 cm/s,附著現象對射流軌跡之比較圖71
圖4.21 不同之密差福祿數(Fo = 25, 62)於ua = 2 cm/s的軌跡變化圖73
圖4.22 ho/D=1,ua = 2 cm/s,附著現象對射流稀釋率之比較圖74
圖4.23 在h0/D = 1下,Fo = 62於ua = 2 cm/s中的稀釋率變化圖76
圖4.24 在h0/D = 1下,Fo = 62於ua = 8 cm/s中的稀釋率變化圖77
表目錄
頁次
表4.1 實驗流況表43
表4.2 實驗流況表44
表4.3 實驗流況表46
表4.3 是否發生附著現象之分類表40
表4.4 實驗於不同橫向流速下,所得之β、θc對應表42


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