本研究以實驗量測方式探討背階入口不同渦流強度對於三維背階流場特性與熱傳效應的影響。使用一小型風洞系統用來產生均勻流之空氣進入管道入口，另一個不同高度的測試管道連接形成一展弦比為4，擴張比1.33，背階高1.75cm的背階管道，於背階後使用厚度0.1mm的不鏽鋼片貼於加熱表面，將三角翼渦流產生器置於管道入口以產生不同渦流強度的入口條件，流場雷諾數介於500至15000之間，包含層流、過渡流及紊流。使用都卜勒雷射測速儀(LDV)及T型熱電偶線量測速度及溫度，量測內容包涵：(1)再接觸長度的量測及背階下游斷面的流場結構。(2)近熱傳面的流場特性，如對流效應、二次流效應及紊流效應。(3)熱傳面的熱傳效應分布。
研究結果顯示，在層流時再接觸長度隨雷諾數增加而增加，過渡流時再接觸長度隨雷諾數增加而減少，紊流時再接觸長度幾乎不隨雷諾數變化，加裝渦流場生器時會使再接觸長度變短，也加快使流體發展成過渡流與紊流。加裝渦流產生器也使得近壁面之對流強度及紊流效應增加，也因此增加了熱傳效應，其中紊流效應為影響熱傳效應的主因。最大熱傳效應發生於再接觸點附近。

The research experimentally investigates the effects of vortex intensity on the flow and heat transfer characteristics in three-dimensional backward-facing step flows. A wind tunnel system is used to generate a uniform flow at an inlet duct. Another test duct of different height is connected to the inlet duct to form a backward-facing step duct of aspect ratio 4, expansion ratio 1.33, and step height of 1.75 cm. A 0.1 mm thick stainless steel foil is attached to the step wall to serve as the heat transfer surface. Vortex generator is placed inside the inlet duct, and used to generate different levels of vortex on the inlet free-stream. The Reynolds number is between 500 and 17000, which cover the laminar, transitional and turbulent flows. The velocity and temperature measurements were conducted using laser Doppler velocimetry, and Type-T thermocouples, respectively. Specifically, the measurements include (1) the reattachment length, and the flow structures at different duct cross-sections downstream of the step wall; (2) the flow characteristics near the heat transfer surface, such as the convective mean velocity, the secondary flow and the turbulent kinetic energy; (3) the heat transfer distributions on the heat-transfer surface. Results of this study show that the reattachment length increases with Reynolds number in the laminar flow region, decreases with Reynolds number in the transitional flow region, and almost remains constant with Reynolds number in the turbulent flow region. The vortex generator much reduce the reattachment length, and the Reynolds numbers for the onset of the transitional and turbulent flows.  This study also indicates that the vortex increase the convective mean velocity, and turbulent kinetic energy near the transfer surface, and cause the increase in heat transfer rate. The flow turbulent kinetic energy plays the most important role in heat transfer distributions. The maximum heat transfer rate occurs near in the reattachment point.

目    錄

摘要......................................................I
目錄......................................................V
圖表目錄...............................................VIII
符號說明................................................XIV
第一章、 緒論.............................................1
   1-1 研究動機...........................................1
   1-2 文獻回顧...........................................2
   1-3 研究目的...........................................7

第二章、 實驗設備及量測儀器...............................9
   2-1 實驗設備...........................................9
      2-1-1 自由流風洞....................................9
      2-1-2 測試段.......................................11
      2-1-3 渦流產生器...................................14
   2-2 實驗量測儀器......................................15
      2-2-1 雷射都卜勒測速儀.............................15
      2-2-2 熱電偶線及I/O tech溫度擷取系統...............18
   2-3 三維精密位移系統..................................20

第三章、 研究原理與實驗方法..............................27
   3-1 研究原理..........................................28
     3-1-1背階流道的特性.................................28
     3-1-2基本參數.......................................29
     3-1-3 渦流強度的計算方法............................33
     3-1-4 應用原理......................................34
   3-2 實驗方法..........................................36
     3-2-1 流場量測方法..................................36
     3-2-2 熱傳量測方法..................................40

第四章、 實驗結果與討論..................................47
   4-1 背階入口之渦流流況................................47
   4-2 再接觸長度之量測..................................49
     4-2-1 軸向再接觸長度隨雷諾數之變化..................49
     4-2-2徑向再接觸長度之變化...........................51
   4-3 X-Y斷面之流場向量分布.............................53
   4-4 軸向近壁面之流場探討..............................54
     4-4-1 軸向速度之變化................................54
     4-4-2 二次流效應....................................55
     4-4-3 紊流效應......................................56
   4-5 徑向近壁面之流場探討..............................58
     4-5-1 徑向速度之變化................................58
     4-5-2 二次流效應....................................58
     4-5-3 紊流效應......................................58
   4-6 熱傳量測結果......................................59
     4-6-1 Nu平均值之比較................................59
     4-6-2 徑向之熱傳發展................................61
     4-6-3自由流與加裝渦流產生器之比較...................62
     4-6-4迴流區內熱傳效應之比較.........................63
   4-7管道中央熱傳結果與近壁面流場比較...................64

第五章、 結論與未來方向.................................151

參考文獻................................................154

圖 表 目 錄
圖1-1 背階管道流場示意圖……………………………………………8
圖2-1 小型自由流風洞系統及測試管道圖………………………….21
圖2-2 背階管道立體圖……………………………………………….22
圖2-3 熱傳測試管道與加熱板示意圖……………………………….23
圖2-4 後掠65˚三角翼渦流產生器構造圖………………………….24
圖2-5 雷射都卜勒速度量測系統示意圖…………………………….25
圖2-6 熱電偶線埋設構造圖………………………………………….26
圖3-1 circulation算法示意圖………………………………………41
圖3-2 Rankine vortex特徵圖(引用自文獻[20])………………….42
圖3-3 X-Y  Z/wd=0(Z=0mm)斷面速度量測位置示意圖…………….43
圖3-4 X-Y  Z/wd=-0.657(Z=-23mm)斷面速度量測位置示意圖……44
圖3-5 自由流近壁面Z/wd=0與Z/wd=-0.657速度量測示意圖………45
圖3-6 溫度量測位置示意圖………………………………………….46
圖4-1 後掠65˚三角翼渦流圖……………………………………….66
圖4-2 渦流中心發展座標圖………………………………………….67
圖4-3 渦流中心十字向量圖………………………………………….68
圖4-4 渦流強度與面積關係圖……………………………………….69
圖4-5 渦流強度圖…………………………………………………….70
圖4-6 管道中心再接觸長度發展…………………………………….71
圖4-7(a) 自由流再接觸長度徑向發展………………………………72
圖4-7(b) 正三角翼再接觸長度徑向發展……………………………73
圖4-7(c) 倒三角翼再接觸長度徑向發展……………………………74
圖4-8(a) 自由流X-Y斷面向量圖 Re=992  Z/wd=0………………..75
圖4-8(b) 自由流X-Y斷面向量圖 Re=992  Z/wd=-0.66……………76
圖4-8(c) 自由流X-Y斷面向量圖 Re=4892  Z/wd=0……………….77
圖4-8(d) 自由流X-Y斷面向量圖 Re=4892  Z/wd=-0.66………….78圖4-8(e) 自由流X-Y斷面向量圖 Re=15840  Z/wd=0………………79
圖4-8(f) 自由流X-Y斷面向量圖 Re=15840  Z/wd=-0.66…………80
圖4-9(a) 正三角翼X-Y斷面向量圖 Re=927  Z/wd=0………………81
圖4-9(b) 正三角翼X-Y斷面向量圖 Re=927  Z/wd=-0.53…………82
圖4-9(c) 正三角翼X-Y斷面向量圖 Re=10321  Z/wd=0……………83
圖4-9(d) 正三角翼X-Y斷面向量圖 Re=10321  Z/wd=-0.42………84
圖4-10(a) Re=992 自由流近壁面軸向發展軸向速度………………85
圖4-10(b) Re=4892 自由流近壁面軸向發展軸向速度…………….86
圖4-10(c) Re=15410 自由流近壁面軸向發展軸向速度……………87
圖4-11(a) Re=927 正三角翼近壁面軸向發展軸向速度……………88
圖4-11(b) Re=1540 正三角翼近壁面軸向發展軸向速度………….89
圖4-11(c) Re=10321 正三角翼近壁面軸向發展軸向速度…………90
圖4-12(a) Re=927 倒三角翼近壁面軸向發展軸向速度……………91圖4-12(b) Re=1540 倒三角翼近壁面軸向發展軸向速度………….92
圖4-12(c) Re=10321 倒三角翼近壁面軸向發展軸向速度…………93
圖4-13(a) Re=992 自由流近壁面軸向發展二次流效應……………94
圖4-13(b) Re=4892 自由流近壁面軸向發展二次流效應………….95
圖4-13(c) Re=15410 自由流近壁面軸向發展二次流效應…………96
圖4-14(a) Re=927 正三角翼近壁面軸向發展二次流效應…………97
圖4-14(b) Re=1540 正三角翼近壁面軸向發展二次流效應……….98
圖4-14(c) Re=10321 正三角翼近壁面軸向發展二次流效應………99
圖4-15(a) Re=927 倒三角翼近壁面軸向發展二次流效應……….100
圖4-15(b) Re=1540 倒三角翼近壁面軸向發展二次流效應………101
圖4-15(c) Re=10321 倒三角翼近壁面軸向發展二次流效應…….102
圖4-16(a) Re=992 自由流近壁面軸向發展紊流效應…………….103
圖4-16(b) Re=4892 自由流近壁面軸向發展紊流效應……………104
圖4-16(c) Re=15410 自由流近壁面軸向發展紊流效應………….105
圖4-17(a) Re=927正三角翼近壁面軸向發展紊流強度……………106
圖4-17(b) Re=1540正三角翼近壁面軸向發展紊流強度………….107
圖4-17(c) Re=10321正三角翼近壁面軸向發展紊流強度…………108
圖4-18(a) Re=927倒三角翼近壁面軸向發展紊流強度……………109
圖4-18(b) Re=1540倒三角翼近壁面軸向發展紊流強度………….110
圖4-18(c) Re=10321倒三角翼近壁面軸向發展紊流強度…………111
圖4-19(a) Re=992 自由流近壁面徑向發展軸向速度…………….112
圖4-19(b) Re=4892 自由流近壁面徑向發展軸向速度……………113
圖4-19(c) Re=15410 自由流近壁面徑向發展軸向速度………….114
圖4-20(a) Re=927 正三角翼近壁面徑向發展軸向速度………….115
圖4-20(b) Re=1540 正三角翼近壁面徑向發展軸向速度…………116
圖4-20(c) Re=10321 正三角翼近壁面徑向發展軸向速度……….117
圖4-21(a) Re=927 倒三角翼近壁面徑向發展軸向速度………….118圖4-21(b) Re=1540 倒三角翼近壁面徑向發展軸向速度…………119
圖4-21(c) Re=10321 倒三角翼近壁面徑向發展軸向速度……….120
圖4-22(a) Re=992 自由流近壁面徑向發展二次流效應………….121
圖4-22(b) Re=4892 自由流近壁面徑向發展二次流效應…………122
圖4-22(c) Re=15410 自由流近壁面徑向發展二次流效應……….123
圖4-23(a) Re=927 正三角翼近壁面徑向發展二次流效應……….124
圖4-23(b) Re=1540 正三角翼近壁面徑向發展二次流效應………125
圖4-23(c) Re=10321 正三角翼近壁面徑向發展二次流效應…….126
圖4-24(a) Re=927 倒三角翼近壁面徑向發展二次流效應……….127
圖4-24(b) Re=1540 倒三角翼近壁面徑向發展二次流效應………128
圖4-24(c) Re=10321 倒三角翼近壁面徑向發展二次流效應…….129
圖4-25(a) Re=992 自由流近壁面徑向發展紊流效應…………….130
圖4-25(b) Re=4892 自由流近壁面徑向發展紊流效應……………131
圖4-25(c) Re=15410 自由流近壁面徑向發展紊流效應………….132
圖4-26(a) Re=927正三角翼近壁面徑向發展紊流強度……………133
圖4-26(b) Re=1540正三角翼近壁面徑向發展紊流強度………….134
圖4-26(c) Re=10321正三角翼近壁面徑向發展紊流強度…………135
圖4-27(a) Re=927倒三角翼近壁面徑向發展紊流強度……………136
圖4-27(b) Re=1540倒三角翼近壁面徑向發展紊流強度………….137
圖4-27(c) Re=10321倒三角翼近壁面徑向發展紊流強度…………138
圖4-28 自由流平均Nu值軸向發展………………………………….139
圖4-29 正三角翼平均Nu值圖軸向發展…………………………….140
圖4-30 倒三角翼平均Nu值圖軸向發展…………………………….141
圖4-31(a) 低雷諾數熱傳效應軸向發展比較………………………142
圖4-31(b) 高雷諾數熱傳效應軸向發展比較………………………143
圖4-32 自由流Nu值徑向發展……………………………………….144
圖4-33 正三角翼Nu值徑向發展…………………………………….145
圖4-34 倒三角翼Nu值徑向發展…………………………………….146
圖4-35 迴流區內平均熱傳效應比較……………………………….147
圖4-36 自由流管道中心Nu值……………………………………….148
圖4-37 正三角翼管道中心Nu值…………………………………….149
圖4-38 倒三角翼管道中心Nu值…………………………………….150

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